3.0 compression test figures

P

peter700

Member
Hi

Although from reading on here it's not uncommon for people to have to top up there engine oil i do seem to be doing it quite often. About .5L per 500 miles. So i though i would compression test it has i need to change the plugs anyway just to see if one cylinder in particular was lower or if all 6 where showing signs of wear. Bearing in mind the car has only just clocked over 47K with a full BMW history i am quite suprised by the oil usage. My previous 3.0 E85 was on 88K when i sold it and i never needed to top it up between services.
My quest is dose anybody who what figures i should be expectting for either a cold or hot engine ? Somebody at work quoted me 170 PSi is this correct ?
 
its not so much the figure thats important but the variation.
If its burning oil it could be the oil scraper rings (which wont affect compression figures) but after 47k they should be ok, i would suspect a gummed up ccv especially if your car has had light use/short journeys.
regards
 
.5L per 500miles is still within tolerance for this engine. The m54b30 is known for that it can burn some oil. It has nothing to do with wear or a clogged up ccv (although a clogged up ccv will cause oil consumption, but in far greater amount).
I stopped my oil consuption by switching to 10w40 oil. That virtually cured it. Apparently the subscribed oil is a bit on the thin side.
I can only think of the longer stroke of the pistons that causes the oil consumption as the 2.2L and 2.5L don't have this problem (it is purely a 3.0L thing) and the stroke is the only thing that differs and can cause oil consumption.
Maybe the cilinders are a bit on the oval side deeper down (fairly common effect as the cilinder head bolts put a strain on the block).
 
Cheers for the replys, I have only just done an oil service on it. I put in castrol egde 5w30, next time i might try putting in 10w40 egde. Most the cars i have owned/ worked on have used 10w40 i did think myself the 5w30 seemed a bit thin.I will post the results of the compression test when i get 5 mins to do it.
 
I discovered it as I wanted to top up again and the gas station only had 10w40 (I think valvoline or so), and I bought 5L, and I gradually had to top up less and less ;)
 
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