Vehicle engine life

[booster]

We often get questions on the forum about the wisdom of buying an older class b. The reasons to do so are certainly valid, be it for initial cost, preferred design, nostalgia, to learn if a b is for you, etc so not a bad choice for a lot of people. We were looking for a used one in 2006-2007 time range for our first b as a test and for cost reasons, but happened on a new one for a price low enough to use it for a test as we would likely lose almost nothing in a year or two if we decided we didn't like it. We still have it though.


What is of interest to me right now on the topic is a trend that I seem to be seeing in everyday vehicles, not necessarily vans or RVs. I have consistently watched Craigslist used vehicles for many years, some out of basic curiosity, but more to keep a feel for what prices were doing and to see what vehicles had repeated issues. Craigslist is a good place to get a feel for the issues because a lot of the vehicles list what repairs have been recently made and are often at the higher end for miles. Head gasket replacement in Subaru vehicles is a good example and happens around 100K in many of them.


The last year or maybe more, I have been seeing a fairly significant increase in vehicles that have a new engine in them or are in need of one. More than I would ever expect say the engine was replaced at less than 100K and often on warranty. Many are not all that old or high miles at all, and it is spread across almost all brands.



I really don't know what is going on, but it is a bit troubling to me as it very possibly being caused by something other than engine designs, although design changes could also be a factor. We saw a lot of timing change issues a few years ago, which seems to have gotten a lot better, and usually wouldn't trash the engine completely, and there were some known issues with the direct injection gas earlier versions, which also seem to be lessened. When I start seeing GM V8s with replaced engines before 100K or others with engines that aren't on the high tech end of the scale failing it is pretty surprising.



One of the issues listed pretty commonly now are engine "knocking" as in rod or main bearing noise, (not pinging type knocks), which for a long time has not been a common problem in less than very high mile stuff. These kinds of failures are most commonly related to lubrication issues like bad oil, low pressure or flow, contamination, etc so that may be part of what is going on.


The manufacturers, as we know, have been stretching out oil change intervals to increasing long periods. We know that oil analysis shows the oil to be capable of doing it and keeping reasonable engine life, but perhaps there are other issues than just time and normal wear particles. Things like condensation, other contaminants like coolant, fuel, EGR soot, etc could certainly cause issues if there, for instance.


GM and I think some others have started moving away from the very small oil filters and back to more full size ones that we saw in the past. It usually is said it is to improve initial cold start oil flow in very cold weather, but cold start wear is not a good/bad switch. If it is destructive in cold weather, it is also going to wearing faster in warmer weather also, but more of a long term failure. There may also be less of a trend to change to thinner oil in the cold now that in the past, but that is just a guess. There is also a chance that oil flows have been reduced in an effort to get better fuel economy.



All the oils have also changed over time, and recently, with reduced antiscuff additives like zinc. Others are added and claimed to be a good or better, but the zinc in particular has a very high protective characteristic on metal to metal contact. It was widely proclaimed that reduced zinc was OK in newer engines because the cams are all rollerized, and the valvetrain similarly protected. You can't use the low zinc oil in non rollerized cam engines, especially at break in, as they will fail quickly. Maybe what we are seeing is the remaining metal to metal contact points like the oil pumps and piston rings and skirts are wearing faster than they should unless everything else is perfect.


There are so few one ton vans showing up on Craiglist that it is hard to tell if they are showing similar trends, especially when they are often commercial use and totally used up by the time the do show up. Hopefully, they will turn out to be among the better survivors.


I think it points out that anyone looking at used class b vans, even newer ones, may need to pay more attention to the engines that we previously thought because there have been such good improvements in engine life over the years. Compression, oil pressure, and leakdown tests can get pretty expensive so probably prohibitive for most prepurchase inspections, though.


For us, we will continue as we are for maintenance, but I tend to be very conservative in maintenance schedules and the larger filters have been used on our Chevy since about the third oil change. It also has an oil pressure gauge to watch for changes, but even with smaller filters we haven't seen lots of failures at all from other users.


I probably will be doing a full drivetrain rebuild on my 96 Buick Roadmaster wagon this winter. It has a 5.7 GM small block, 4L60e trans, and typical rear drive axle. Currently at 140K and not using oil, but is leaking so time do it up completely as long as I need to pull it to fix the leaks. It will be very interesting to measure all the wear in the engine dimensions to see how it held up. The oil pump will be of particular interest to me, to see how worn it is and if it has been replaced before. It appears to have good care for the 15+ years before I got it, but the wear should say for sure. It is rollerized cam, non rollerized, (bathtub) rocker arms, timing chain setup, so should be fairly similar to what our van would be internally. It also will be interesting to see if it has been opened up in the past, as you usually can get a good idea as you disassemble and check the parts.


Interesting stuff, but it probably would be even more interesting to see what kind of things are causing the early failure by conducting some "autopsies".

[mkguitar]

the GM vortec has many online complaints of piston slap.

I have the 6.0 in the 2005 chassis van at just over 100k. this van requires emissions every year and the test numbers are fantastic running on the dyno: 0 HC/ 0% CO loaded at 37 mph, at idle 1ppm HC and 0% CO

Emissions can be a great indicator of engine health and piston/cylinder seal- MPG and oil consumption too ( zero)

I'm hopeful, my experience with my truck influenced my decision to buy the van at 8 years and 80k

The 2001 pickup has good emissions at 170k.
This has the 4.8L vortec and it demonstrates after a few minutes on a cold start -a knock, a noise at speeds below 1000 rpms started about 80k- it hasn't really changed and hasn't been tracked- it could be external -
-water pump, idler and serpentine changes made no difference
( at one time the steering pump was suspect)

I have had intermittent issues with front knock sensor- apparently related to a bad ground- fixed(?)- it appears good w/ scanner- no CEL past year.

Emission tests remain good- great even, so change in MPG or any sensor reading which indicate an issue.
All in all this truck still provides 20 mpg and the only mechanical repairs have been 2 water pumps and a fuel pump.

sparkplugs, tires, wipers, gas filters, and lots of mobil 1, generally changing at about 3000 miles. I do have some front end wear/slop coming on.
Arizona is hard on rubber parts, but at least there is no rust on the fasteners when it's time to change them.
This truck also has the factory ceramic brake pads...I bought pads at 60,000 miles, and pulled the wheels, no need to change...the pads sit in the garage waiting- I inspect regularly.
Shop tells me GM used Korean ceramics 2001~2003 & they last forever.

I drove taxi in college- at the time the gm 350 was assumed to be done at 150,000 miles and a 78 Ford on which I put 178,000 miles was remarkable in that the 460 had no issues ( 6 mpg)...the dodge dart with 318 was considered the taxi champion.


Outlier: my '67 GMC 292 had 478,000 miles when I sold it- never a fix


Mike

[SteveJ]

My thoughts are that is due to a lack of maintenance. From what I hear, some folks never change the oil in their vehicles. Maintenance free for "the life of the engine".

My 2000 RT has 215k miles on the 5.7. Oil, 5w30 synthetic, generally SuperTech of Rural King, gets changed at 5-7k miles. It goes about 4k miles on the first quart, thenuses a bit more, adding a quart or two depending on how hard it works, temps, and the price of tea in China.

So far, the engine has performed flawlessly in the almost 100k miles that I've owned it.

[TygerMark]

My 1978 GMC pickup 350CID got 318,000 miles before the oil pump went. Oil change every 3,000 miles.

Rebuilt it.

[SteveJ]

I used to have a route sales job back in the mid 70's. The vehicles in the fleet consisted of 1 ton Chevies with a freezer box on the back. The drive lines were 350 engines with a manual transmission. The average engine life at that time was 250k miles, not bad for old tech engines.

[avanti]

I'm afraid I am going to have to question the premise on this one.

Informal impressions are fun, but all the systematic data that I am aware of belies the claim that vehicles are becoming less reliable, either in general or with drivetrain issues in particular. It is certainly true that the average lifetime of cars on the road just keeps going up. This is a different measure from actual reliability, but they are obviously closely related. A typical historical dataset tends to look like this one:



Consumer Reports says that the percentage of vehicles with reported major engine issues is 1% or less all the way back to MY2012, at which point it goes up to 2%.

https://www.consumerreports.org/car-...ity-histories/

There are many, many sources of such data, and all the ones I have seen suggest that vehicles have never been as reliable as they are today.

[I just wrote and then deleted a long rant about people who think that OEM oil change intervals are nonsense. The last thing this list needs is an oil war. I can get plenty of those over at Sprinter Source.]

[mkguitar]

Oil? on any forum- I'm sure the sewing machine people argue about oil.

My instructor at school ( with a decades long career in NHRA racing and chevy dealer tech + teaching) said "oil is cheap"
Just change it
if you live where it is hot and dusty change it more often. Then recycle the oil.
Don't forget the tranny- after the first messy change, replace the pan with one with a drain

[Davydd]

Growing up in the 50's it was common belief an engine was shot at 50,000 miles and had to be rebuilt. 100,000 miles was ancient. Maybe I was jaded in my belief. My dad bought a new car just about every year.

[booster]

Originally Posted by avanti

I'm afraid I am going to have to question the premise on this one.

Informal impressions are fun, but all the systematic data that I am aware of belies the claim that vehicles are becoming less reliable, either in general or with drivetrain issues in particular. It is certainly true that the average lifetime of cars on the road just keeps going up. This is a different measure from actual reliability, but they are obviously closely related. A typical historical dataset tends to look like this one:



Consumer Reports says that the percentage of vehicles with reported major engine issues is 1% or less all the way back to MY2012, at which point it goes up to 2%.

https://www.consumerreports.org/car-...ity-histories/

There are many, many sources of such data, and all the ones I have seen suggest that vehicles have never been as reliable as they are today.

[I just wrote and then deleted a long rant about people who think that OEM oil change intervals are nonsense. The last thing this list needs is an oil war. I can get plenty of those over at Sprinter Source.]

I am certainly not saying the data is correct, consumer reports tends to be one of the better collectors of data, but they don't go back very far in age compared to what they used to. This is a casual observation, no doubt, and from a single source, but over the years stuff has shown up pretty regularly on Craigslist and when checked out was pretty accurate for things like this.


I think the historical data to look at has to be the repair % for particular areas per year and all the different ages and mileages to be really representative. OEMs have all that data and most general repair shops also have lots of opinions on it.



All I am saying is that there are way more engine failure cars on Craigslist and a very large increase in ones that are not very old or high mileage per my non statistical observation.



One thing that I thought of after writing the original post is that here in Minnesota at least, we are seeing lots of "no rust" "low miles" vehicles just up from Texas in particular. Low mile cars from out of state are always suspect because the low miles was because they were sitting waiting for insurance payoffs and autions. While we always had some of the southern cars show up, they were usually not the daily driver type stuff that is around now. I have a strong feeling that a lot these vehicles are flood cars with scrubbed or never declared salvage titles, as that is very easy to do. I think it is a real possibility that some or many of the engine failure vehicles may also be scrubbed title but with seeing a location history hard to tell. Flood cars are very prone to drivetrain failures if it was deep enough to get in the engine and other driveline areas.


One of the latest observations I found was that there were a number of Honda CRVs, which in general have been very reliable per most everyone, were listed as using a bit of oil in not really old or high mile cars. When I looked into it further, as DW has a 2009 (really a very late 2008 though), I found out it was model year specific to only 2010 and 2011 years and there was even a Honda "silent" recall for only those who complained and the vehicle failed a Honda done oil consumption test. DW was glad to hear that it wasn't hers, though. The cause, as stated by Honda was that in cold weather starts, if the engine is revved to soon and too high (unspecified how much is too much) they could get cylinder wash with fuel causing too little lubrication on the rings and cylinder walls causing excess wear. These would be 10 year old vehicles so I don't know how much detailed tracking of repairs is done that far back.


As I said, nothing conclusive, definitely puzzling, and certainly would make me a more careful used vehicle shopper, especially in the history area for location.

[booster]

Coincidence in that I looked at Craigslist after writing the last post and ran into this one, which is kind of typical of the Texas vehicles we are seeing now, yep, and including where it is being sold from.


https://minneapolis.craigslist.org/d...186512663.html

[wny-pat]

Originally Posted by booster

One of the latest observations I found was that there were a number of Honda CRVs, which in general have been very reliable per most everyone, were listed as using a bit of oil in not really old or high mile cars. When I looked into it further, as DW has a 2009 (really a very late 2008 though), I found out it was model year specific to only 2010 and 2011 years and there was even a Honda "silent" recall for only those who complained and the vehicle failed a Honda done oil consumption test. DW was glad to hear that it wasn't hers, though. The cause, as stated by Honda was that in cold weather starts, if the engine is revved to soon and too high (unspecified how much is too much) they could get cylinder wash with fuel causing too little lubrication on the rings and cylinder walls causing excess wear. These would be 10 year old vehicles so I don't know how much detailed tracking of repairs is done that far back.

Neither of my Honda's use any oil between changes. My CR-V is a 2014 and my Odyssey is a 2016. I use the mileage minder for oil changes and both are around 9 to 10,000 miles between changes. Use Schaeffer's 0w20 synthetic. Oh, the CR-V does have the VTC grinding noise on cold start up. My research on the issue shows the even after replacing the VTC, they still have the problem, so I'm leaving it alone.

[booster]

Originally Posted by parmm@atlanticbb.net

Neither of my Honda's use any oil between changes. My CR-V is a 2014 and my Odyssey is a 2016. I use the mileage minder for oil changes and both are around 9 to 10,000 between changes. Use Schaeffer's 0w20 synthetic.

Not surprising at is was limited to 2010 and 2011 CRVs only AFAIK. DW's CRV is fine and it 12 years old now.

[Belzar]

Campers are not good measures of how long engines last. An engine, or just about any mechanical device, works best if operated regularly. Campers tend to sit for long periods of time A decades old low mileage camper is likely to have more issues than a higher mileage one that has regular use and maintenance. It is unrealistic to expect a quarter century old (mid-90's) lightly used camper to not need significant engine work.

[peteco]

Originally Posted by Belzar

Campers are not good measures of how long engines last. An engine, or just about any mechanical device, works best if operated regularly. Campers tend to sit for long periods of time A decades old low mileage camper is likely to have more issues than a higher mileage one that has regular use and maintenance. It is unrealistic to expect a quarter century old (mid-90's) lightly used camper to not need significant engine work.

One nice thing about our B while at home is I use it 2-3 times a week for local trips. That keeps it "exercised" without putting excess miles on it.

[booster]

I did a bit of reading, expanding around the Honda issue mentioned earlier and it brought up some, at least to me, interesting issues with newer engines.


With some of the Honda models that also got some issues with oil consumption, it was mentioned that the use of "low quality" fuel could cause/contribute to the problem. This is not the same as cold engine fuel wash causing lubrication reduction. The same type of fuel quality issues were also mentioned with other brands of engines also.


I think most of us have heard of fuel quality issues related to intake valve/runner deposits, stuck or leaking intake valve things, mainly with high end high performance stuff, but that wouldn't cause stuck rings, which is what the oil burning seems to be related to and is the fix for it by replacing the rings or rings and pistons.


What appears to be said is that the low quality fuel is causing more deposits on the pistons and rings, eventually making the rings stick and not make good contact with the cylinder walls.


The reason given that this is a fairly recent, 10 years?, issue is that the big push to improve fuel mileage changed some design parameters in the piston and rings. To reduce friction, most of the rings are much narrower now, maybe 1.5mm instead of 2.0mm (basically the same as going from 5/64" to 1/16" rings which has bee common in race engines for a long time). The narrow rings are less able to seal the combustion so more prone to getting buildup that leaks though and fouls the rings, grooves, and even the piston surface on main diameter. My guess would be that a lot more of the compression is being held by the second compression ring than in the larger ring systems which means more buidup between the top and second ring. Second rings are significant final oil scrapers so can have a big impact on oil use.


Using higher quality gas, usually with very high detergent levels, there is less to build up on the rings. Secondarily, there was a lot of mention of lack of maintenance, primarily oil changes, so they must be counting on clean oil helping keep the rings cleaner, which makes sense, and we know lots of people abuse the oil change schedules even as long as they are now.


Not mentioned, but that I think may also be a factor is the EGR valves and how much they are open, as well as how uniformly they dilute the aircharge. It appears when the EGR is open, there is a need to reduce the amount of fuel as there is less oxygen to burn, and they also need to increase the timing because the mixture is less combustible and is slower burning. With all the issues with EGR valves plugging, sticking, etc, there is quite a bit to go amiss there and cause bad mixture. Pinging when the EGR is open is very common with some vehicles, so I would guess being slightly rich would also be pretty common on those that don't ping.



In regard to the previously mentioned "piston slap" comment about the GM LS series engines being will known for it, it is certainly true, although the slap is often blamed for hydraulic lifter noise, exhaust manifold leaks, or wrist pin noise so probably not quite a common as some say.


The piston slap is also related directly to the stiff that is mentioned about for the oil use in quite a few ways. The new engines are using shorter pistons, so much less skirt to stabilize against piston rock angle which make the slap louder and also lessens ring sealing. It is being done to reduce piston thrust friction and is another of the old racing engine things. They also have been reducing the wrist pin offset to very low levels in new designs like the LS engines. The only reason the offset is there is to reduce piston slap, but it causes a bit more friction while doing that noise reduction. Low/no offset engines with be more noisy, get better fuel mileage and make more horsepower, so good and bad. With the low offset pins and short skirts, the engineers stated that if an engine was on the tighter clearance tolerance end of the dimensions, it would be quiet, but on the higher end of the tolerances it would have noticeable slap, which is just what we see in the GM stuff. Not everybody has piston slap. Slap that goes away once warmed up is generally not considered a factor in engine life or oil consumption, but IMO if it is slapping because it is on the high clearance tolerance end, it will almost certainly hit wear limits sooner and that would mean some amount of shorter life.



Then, on top of all of the above about piston slap reasons for happening more now, another big factor is that it is now easier to hear in many engines due to block designs and materials. Aluminum blocks transmit much more noise, so more noticeable slap, than cast iron blocks. Apparently, the thinner the steel cylinder liners, the louder they get. This may explain why I don't recall hearing much about LS 6.0 engines in the vans in relation to slap, as they have cast iron blocks, while the lighter duty LS engines have aluminum.


This information all makes some real sense to me, particularly if you go way back to the 1960s engines that were also a bit famous for oil burning due to stuck rings, although back then it was primarily caused by low quality oil, not changing the oil, issues fouling the oil and second rings. We used to routinely reduce the oil consumption on these engines by pulling the plugs and filling them with kerosene mixed the engine top cleaner and let them sit. I bought a used Valiant with 225cid six cylinder while in college and it use a quart in 100 miles. We did the cleanout and it went up to over 1000 miles, so it can be a big deal if you have stuck rings. It only had 70K miles on it.



I think the bottom line would be the same thing that a bunch of already do IIRC. Buy top tier gas, change your oil regularly, don't get on the throttle hard until the computer goes closed loop (they start and cold run in open loop, which is typically quite a bit richer than closed loop running on the oxygen sensors. If you live in a cold climate and use the vehicle for errands, make sure you drive on highway to get the oil temp up to take out the moisture. Around here that can take at least 1/2 hour in cold weather. (MN)


Just as a point of reference on the tolerancing of engine parts. On the engine I am going to build for my old Buick, which is a LT1 gen2 5.7 liter with cast iron block and heads, the piston to wall total clearance at the prescribed measuring point is called out at .0015" to .0020". This gives a total of .0005" of tolerance to be used in 8 different cylinder over their full height so diameter and taper, plus the diameter of 8 different pistons. These are the piston specs from the aftermarket, higher end, piston supplier for hypereutectic cast aluminum pistons which are some of the lowest heat expansion ones you can get. Most of the good high performance shops even have to individually match the block bore size when honing them to individual pistons that have to go in that cylinder to hold that kind of tolerance or better. I would have to pull the factory setup specs for that clearance, but I am sure the range is much more. Add to that you have similar tolerance desires on the top and second rings to hold the optimum end clearance, so those need to be individually matched to cylinder they will go into to minimize combustion leakage but not bind when hot. All the individual matching and fitting is what is what is entailed in a good "blueprinting" of an engine that we often hear about, but in general what is done is adjust the dimensions to give the important stuff like clearances and flatness. Any engine that is fully within the blueprint dimensions in the factory service manual can be quite a ways off of the being in the optimum area of the important stuff.

[SteveJ]

Our main car is a 2018 Kia Soul with the 2 liter non turbo direct injection engine. Checked around and learned some stuff about it. The use of Top Tier gas helps in a lot of ways for this engine and it is recommended in the owners manual. However, it will not clean the intake tract as the fuel does not go through there. I and some others have put oil catch cans in the PVC system to help keep deposits down. It must work as I do get a bit of oil in it.

Also it seems to be important to run synthetic oil with a rating of SN+, not just SN. This oil allegedly reduces the fuming of the oil.

I also use the CRC intake cleaner at 10k mile intervals. The EGR valve will be replaced every 20k miles, cheap and easy.

Oil changes happen at 5k mile intervals.

I also check the oil from time to time.

Some folks have had issues with the Kia motors expiring early(along with fires), a lot of it seems to be lack of aggressive maintenance.

[booster]

Originally Posted by SteveJ

Our main car is a 2018 Kia Soul with the 2 liter non turbo direct injection engine. Checked around and learned some stuff about it. The use of Top Tier gas helps in a lot of ways for this engine and it is recommended in the owners manual. However, it will not clean the intake tract as the fuel does not go through there. I and some others have put oil catch cans in the PVC system to help keep deposits down. It must work as I do get a bit of oil in it.

Also it seems to be important to run synthetic oil with a rating of SN+, not just SN. This oil allegedly reduces the fuming of the oil.

I also use the CRC intake cleaner at 10k mile intervals. The EGR valve will be replaced every 20k miles, cheap and easy.

Oil changes happen at 5k mile intervals.

I also check the oil from time to time.

Some folks have had issues with the Kia motors expiring early(along with fires), a lot of it seems to be lack of aggressive maintenance.

Just an interesting thing to throw out that the higher detergent fuels are said to do on the single injector (into the cylinder) DI engines. All engine have a bit of intake reversion flow that happens right as the intake valve opens as that event happens when the piston is before top dead center. The exhaust valve is also still open then in what is known as the "overlap" area of the valve timing. What is said to happen is that the exhaust pushes the intake charge and some exhaust back past the intake valve and that is what puts deposits on the intake valve and some of the intake manifold. This doesn't happen on port injected engines even though they have the same overlap setup because the fuel spray immediately cleans the intake and valve. DI engines have now mainly gone to adding a second injector in the port to do this in the DI engines. I assume the Top Tier gas would help a single injector DI engine because their would be less things in the exhaust to mess up the intake valve, or the detergents also work once burned. I don't know exactly where in the cycle they inject the cylinder but probably is after the exhaust valve closes.


There are also filters you can put inline for the PCV valves so the fumes don't get away, but you catch heavier blowby particles of oil, which are getting more popular these days, for just the reason you state. Anything the makes deposits is not good to have in the incoming air, be it blowby oil or EGR fumes.

[wny-pat]

Originally Posted by booster

I did a bit of reading, expanding around the Honda issue mentioned earlier and it brought up some, at least to me, interesting issues with newer engines.


With some of the Honda models that also got some issues with oil consumption, it was mentioned that the use of "low quality" fuel could cause/contribute to the problem. This is not the same as cold engine fuel wash causing lubrication reduction. The same type of fuel quality issues were also mentioned with other brands of engines also.

Mainly caused by Variable Cylinder Management which can be permanently fixed with a aftermarket VCM disabler. There was also a recall for the problem if you had the right year, but the problem comes back to visit again.

[booster]

Originally Posted by parmm@atlanticbb.net

Mainly caused by Variable Cylinder Management which can be permanently fixed with a aftermarket VCM disabler. There was also a recall for the problem if you had the right year, but the problem comes back to visit again.

I did see some on that about cylinder disable oscillating on and off rapidly at light throttle cruise, which certainly would do bad things. I think that was only on the V6 engines though IIRC. I don't think any of the CRV 4 cylinders disable at all. The recalls did seem to be pretty random compared to complaints for all the different models that had issues, but six and four cylinder models. I think the recalls were mainly software flashes and the silent warranty was a variety of new rings, pistons, and whole engines.

[SteveJ]

Originally Posted by booster

Just an interesting thing to throw out that the higher detergent fuels are said to do on the single injector (into the cylinder) DI engines. All engine have a bit of intake reversion flow that happens right as the intake valve opens as that event happens when the piston is before top dead center. The exhaust valve is also still open then in what is known as the "overlap" area of the valve timing. What is said to happen is that the exhaust pushes the intake charge and some exhaust back past the intake valve and that is what puts deposits on the intake valve and some of the intake manifold. This doesn't happen on port injected engines even though they have the same overlap setup because the fuel spray immediately cleans the intake and valve. DI engines have now mainly gone to adding a second injector in the port to do this in the DI engines. I assume the Top Tier gas would help a single injector DI engine because their would be less things in the exhaust to mess up the intake valve, or the detergents also work once burned. I don't know exactly where in the cycle they inject the cylinder but probably is after the exhaust valve closes.


There are also filters you can put inline for the PCV valves so the fumes don't get away, but you catch heavier blowby particles of oil, which are getting more popular these days, for just the reason you state. Anything the makes deposits is not good to have in the incoming air, be it blowby oil or EGR fumes.

The oil catch can that I installed does have convoluted passage ways to catch the droplets. I believe it also has a course filter in the housing.