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Old 07-15-2015, 10:08 AM   #1
busy
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Default compression ratios

Hello, another question, my eos uses a fair bit of oil, it says in the book up to 1ltr per 1,000 kms , so I am wondering what the compression readings should be, its just coming up to the end of the warranty so if they are down its best to know now rather than later.
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Old 07-15-2015, 10:17 AM   #2
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No car details, how can you get your question answered? My TDI diesel has a very high compression ratio.

It's not really compression ratio that affects oil burn anyway. It is the condition of the oil control ring(s). If your car has done very little high speed cruising mileage, then expect oil consumption to be higher if the engine is gummed up with carbon.
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Old 07-15-2015, 12:08 PM   #3
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Quote:
Originally Posted by voxmagna View Post
No car details, how can you get your question answered? My TDI diesel has a very high compression ratio.

It's not really compression ratio that affects oil burn anyway. It is the condition of the oil control ring(s). If your car has done very little high speed cruising mileage, then expect oil consumption to be higher if the engine is gummed up with carbon.
Hi Voxmagna, I'm sorry for not posting the details, its a 2.ltr petrol tfsi 200 bhp turbo model manufactured in oct 2007 with a dsg gearbox.
Would there be a difference in compression if the rings say, on one bore was letting past. would the other 3 be slightly higher, I dont get to motorway very much but only did 500 miles and had to put 1ltr in. I then zeroed and did 450 miles and there was about a quater showing on the dipstick, so had used 3/4 of a ltr for 450miles.
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Old 07-15-2015, 01:05 PM   #4
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There is a myth around that most modern engines burn more oil these days. True, one factor is using wide viscosity range synthetic oils will get more bore ring leakage. But the biggest factor is how the engine was driven when first new and subsequent mileages. Modern production methods produce close tolerance cylinder bores consistently and much more easily. Marry that to high performance lubricants and engines babied from new may never be run in (worn in) for 20 K miles or more. As engine size and power goes up, the problem gets worse because the engine is hardly ever producing its full output for extended periods of time. Drive any rental car - they never use oil!

I discovered this when I tore down a modern 2 liter car that had only done 15K and was burning a lot of oil. The owner used the car mostly for short commutes and shopping as a 'careful' driver. The piston rings were so gummed up with carbon they were stuck solid in the piston grooves. If that owner had been a bit of a 'Boy Racer' the car would have been better for it.

I'm not a great fan of pouring ingredients into the gas tank, but engine cleaners work by raising the running temperature in an attempt to burn away stuck carbon. Run tank down to 1/4, pour it in and then do a hard drive at 70 mph in 1 gear lower to keep the revs up.

There is another possibility and that is oil leakage past the turbo seals. I'm not sure how you distinguish that from piston rings though. Turbo rebuild firms will give you opinions based on car mileage as to how long they think they last.

Unfortunately, there is nothing hard to go on for a warranty claim and I suspect you will be told 'Some cars use more oil than others and that's normal Sir'.

If you check the color of each spark plug it may give clues if one is particularly sooted due to excessive oil burn on that cylinder.
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Old 07-16-2015, 10:27 AM   #5
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well it turned out fine, they were all between 200 on the center ones and 210 both ends. no sooting on plugs, so it just uses that much oil. I do use on short trips a lot so maybe it's because of that, there is no smoking from the exhaust and if leaking past turbo seals wouldn't there be a bit of burnt oil showing on the exhaust, my exhaust tips are that nice dark reddish colour.
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Old 07-16-2015, 03:18 PM   #6
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Oil used = oil leaked or burned. Simple equation.

Next oil change, if you can find a higher viscosity compatible VW spec. oil, try that and compare, even if it is not Long Life.

Synthetic oils do not burn so black like dyno oils.
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