Topic: Auto Tech: Oil consumption

[Autos_Editor]

Master mechanic Jim Kerr examines the reasons why some engines consume more oil than they should and what the solutions, if any, are.
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[mike t]

Great article, Jim.

Sometimes oil leaks from a worn valve cover gasket. If the leak is slow enough, it'll burn off and won't make it down to the ground. So checking under the hood for messy areas is another way to spot an oil leak.

[blur911]

Some engines also just use oil normally.  I believe the normal consumption rate for my old 911 is something like 1 liter/1000miles, more if used at the track.  (it's right in the owners manual)

[Railton]

Some engines also just use oil normally.  I believe the normal consumption rate for my old 911 is something like 1 liter/1000miles, more if used at the track.  (it's right in the owners manual)

Is this the case with new 911's as well Caymans and Boxsters?
Railton

[D70]

Very good coverage of the subject.
Over 50 years of owning cars I have owned every example.

 My first car had the engine rebuilt, I had a 40 gallon drum of waste oil and skimmed the good stuff off the top. This worked until the motor expired and the rebuild solved everything and restored the engine to new like performance

http://www.flickr.com/photos/d70w7/4447872084/

 My present daily driver, a 1990 Miata, had a used $750 motor installed, cheaper than the new crankshaft that was required when I purchased the car. 3 years later massive oil leaks resulted so it was pulled and everything replaced with new seals, no more leaks.

http://www.flickr.com/photos/d70w7/4867838400/

 My 10 year old Oldsmobile Intrigue with a DOHC 4 valve per cylinder V6 uses oil to the rate of about .5 of a liter per 5000 km. Absolutely no leaks and has done so since I bought the car with 22,000 km. I find that is acceptable.

http://www.flickr.com/photos/d70w7/1599268396/

 My V twin DL650 Suzuki uses no oil  between changes.

http://www.flickr.com/photos/d70w7/4716945999/

All my other cars had no leaks and no oil consumption. I know from friends that BMWs used oil in the past and Mazda rotarys have to use oil, its the way they run, part of the lubricating system.

[Jim Burns]

I hada car that started exhibiting odd oil leaking in its final moments before it was sold off.

One day when checking the oil level, I noticed one of the spark plug caps wasn't seated properly. Upon removal, I noticed the spark plug cap was engorged in engine oil. I re-seated it and some oil oozed out.

Turned out that the valve cover gasket was starting to go, but the engine wasn't consuming any oil. I didn't bother fixing it when I sold it, but I just told the new owner about it. They weren't concerned.

[ktm525]

The only car I owned that used oil in any significant quantity was a Datsun pickup but it had 275 000kms on it. I was told that if an engine was not broken in properly then the rings wouldn't seat causing excessive oil consumption (ie too delicate of break in). Wide open throttle pulls while breaking in an engine would allow the rings to seat. Just watch the RPM. This is what I have done with every new engine and I have not had an oil burner yet.

[tpl]

Our FIT uses none between changes which turn out to be once a year and 8000 km. The GTI uses about 1/2 litre every 8000 km although I checked it at the weekend and it was an exact 1/2 litre down... as it had been in for a service only 1600 kms before I'd wonder if they did not allow for the filter when putting the new oil in.

My BMW used a 1/4 litre every 1000km until it got to about 25000 km at which point it stopped using any measurable amount. Interestingly that consumption would have put the low oil light on just as it would have got to one of BMW's 25000 km services...I never asked but I bet I would have been told " They all do that sir"

[PJungnitsch]

GM has wrestled with this for a while with some of their V8's.

One of my co-workers had her 2006 GM pickup suddenly start using a liter of oil every 500 km at 110,000. Luckily she had extended warranty but the service dept could not figure it out for the life of them. Replaced the pistons, block, no good. She was getting pretty sick of the repeated failed fixes (and changing O2 sensors, which don't like to be bathed in oil).

Finally a TSB came out that pointed it to excessive oil getting pushed to the heads in some engines and then sucked into the engine via the PCV system. New valve covers that shielded the PCV system better from was some of the fix, plus another mod that reduced the oil throw up to the head.

[toolatecrew]

I've only owned 2 cars that use any appreciabble amount of Oil. An RX7 which drank oil like a 2 stroke and my current GTI which seems about on par with TPL's. Oil change intervals are long so you really need to watch it as it can esily be down a full litre between changes. I have to say I don'tmuch care for it but the forums are rampant with owners who have Vw claim its well within their tolerance.

[johngenx]

Older German engines used large tolerances and heavy oil (put 5W-20 in a BMW M30 engine and you'd kill it) with large crankcases or dry sumps.  They didn't use tons of oil, but certainly some.  The 2.6L in my 190E used about 2L between changes during the winter when I used thinner oil, but that was at 500K!

So, I was used to having to top the oil off a time or two between changes.  By the time Mercedes made the M111 four banger in my 98 C230, tolerances had shrunk, and I was actually a little freaked when it hadn't used a single drop during the 250K it lived with me.

For leaks, the 1.8L Honda engine in our Acura Integra was awful.  The cam end seal and valve cover gasket went out constantly.  By 150K, that engine was a sieve.

[safristi]

..any data on what being down half a litre OR a full litre does to an engine?.....and being as much OVER-FILLED.................

[Spheric]

I was word searching the article for 'turbo' and couldn't find it, so my question about why the 2.0T FSI engine in my 07 Passat would need an additional quart of oil every 3000 kms remains unanswered.

Since switching over to the normally aspirated 5 cylinder powerplant, it's been fine and not a drop added to date.

[toolatecrew]

I was word searching the article for 'turbo' and couldn't find it, so my question about why the 2.0T FSI engine in my 07 Passat would need an additional quart of oil every 3000 kms remains unanswered.

Since switching over to the normally aspirated 5 cylinder powerplant, it's been fine and not a drop added to date.

Don't know how cedible this is but this forum claims that the FSI engines have loose piston clearance from the factory. Engines that are reringed under warranty with new higher tolerance ones apparently don't use oil.
http://www.golfmkv.com/forums/archive/index.php/t-91745.html

The more I read the more I think I better keep some detailed records between know and my next service.

[tpl]

..any data on what being down half a litre OR a full litre does to an engine?.....and being as much OVER-FILLED.................

Overfilled can be worse than underfilled.

Under filled: say down to 1/2 full which may be below the bottom of the dipstick. The oil will get hotter which is bad but with modern oils especially synthetics not immediately fatal.  Its possible that under hard cornering  or braking that the oil pickup may get a gulp or air not oil. This is bad.

Overfilled: The crankshaft can hit the oil surface filling the crankcase with foam and leaving air bubbles in the oil.   Oil pumps don't pump bubbles well ( That old crime story thing about injecting the bubble of air into the IV tube...) and that could be a bad thing if it persists. Also its likely that some of the engine seals will be submerged in oil which they may not be designed to be and may start to leak... at the least that can be expensive.

[johngenx]

If you overfill the crankcase, you can cause cavitation of the oil, which is highly abrasive and will eat through main seals in no time.

[Spheric]

I was word searching the article for 'turbo' and couldn't find it, so my question about why the 2.0T FSI engine in my 07 Passat would need an additional quart of oil every 3000 kms remains unanswered.

Since switching over to the normally aspirated 5 cylinder powerplant, it's been fine and not a drop added to date.

Don't know how cedible this is but this forum claims that the FSI engines have loose piston clearance from the factory. Engines that are reringed under warranty with new higher tolerance ones apparently don't use oil.
http://www.golfmkv.com/forums/archive/index.php/t-91745.html

The more I read the more I think I better keep some detailed records between know and my next service.

Thanks for the link. Very informative.

[No H2O]

Some engines also just use oil normally.  I believe the normal consumption rate for my old 911 is something like 1 liter/1000miles, more if used at the track.  (it's right in the owners manual)

That is a maximum which is also stated in my BMW motorcycle owner's manuals. Air cooled engines tend to use more oil.

Other engines that don't burn oil...just don't, or their oil is being diluted which is bad news.

I know that it took almost 20,000 kms for the cylinder walls/rings to wear in on my BMW motorcycles. My 993 uses no oil since I replaced those leaking valve cover seals. My Honda CR-V with 191K kms uses no oil between 10K km oil changes.