Smoke from oil cap?

1995 525i 160k miles

Today I popped my hood while the engine was at regular operating temperature (for what it's worth, it was cold today) and I noticed white smoke coming from under the oil filler cap. Not smoking like a chimney, but enough to be easily noticed. Drove about a mile and popped the hood again, still white smoke but very little, hardly noticeable. Could this be a possible blown head gasket or worn piston rings? Besides checking the compression, is there anything I should look for? Wish I was familiar with this car so I could tell if it was loosing power. According to the OBC, I'm getting ~18 mpg. Thanks for the help and advice guys!

That is not uncommon, especially if you are using thinner oil. It vapourises more easily. No issues, but check oil levels every 2 weeks via the dipstick just to be on the safe side.

Your fuel economy sounds a little low for a vanos car. What is your driving mix ? Driving style ? Is it a fair read...you just bought this car, you might have been revving it all over the place

Hm, will do. As always, thanks a lot for the help roberto! And no, I drive it like a grandpa most the time, with the exception of turning into traffic and such, usually I'm sitting at about 2-3k RPMs.

City / highway ratio sir ?

Your ride may need a tuneup. An italian tuneup.

It has NOTHING to do with how "thin" the oil is and, your oil certainly is not vaporizing.

Are you seeing this smoke when the cap is still on, or when you remove it? If crankcase vapors are getting past the cap, you have a problem. If you pull the cap on a hot engine, on a cold day, I would fully expect to see water vapor condensation. It is the same as seeing your breath when it is cold. Hot air contains more water, when it hits cold air it condenses creating white "smoke".

Very unlikely that this is a problem. Doing a compression test should give you piece of mind but probably isn't necessary.

All city mileage. And it is while the oil cap is on and tightened, that's what strikes me as odd.

Oh dear my mistake, did you mean smoke while the cap is still on ??

Bad cap ! Can also be responsible for idle problems and poorer mileage. Please get a new cap.

+1 on being normal when the cap is OFF. If smoke is exiting with the cap on, time for a quick and simple R&R of the oil cap.
Maybe your car does need a tune-up though. you do not have an Italian car, please do not perform an Italian tune-up. Do a PROPER tune-up for a proper car.

Sent from my ADR6410LVW using Bimmer App

you have your answer man.

I would just replace the cap. it's not sealing right. thats all.if it persists with a new cap, then i would worry about leak-down tests and all that.


Roberto: 18mpg is exactly what an M50TU will do. 248K miles worth of it for this guy.

Originally Posted by 95 E34

you have your answer man.


Roberto: 18mpg is exactly what an M50TU will do. 248K miles worth of it for this guy.

Yes Padre I agree. As the OP pointed out later, his driving is all city, in which case 18mpg is a fair number. Usually when MPG figures are quoted, the unspoken assumption is 50/50 driving and if this is not the case, it should be explicitly stated. I believe Steve gets as high as 28 mpg (from a response to one of the first threads I started on the forums) on his vanos E34 but he does alot of highway driving.

Originally Posted by goosefoot33

+1 on being normal when the cap is OFF. If smoke is exiting with the cap on, time for a quick and simple R&R of the oil cap.
Maybe your car does need a tune-up though. you do not have an Italian car, please do not perform an Italian tune-up. Do a PROPER tune-up for a proper car.

Sent from my ADR6410LVW using Bimmer App

Italian tuneups emerged from the 1960s and 1970s when oil and engine technology was significantly poorer which resulted in alot more carbon caking the engine in places. This was a quick and dirty way to exercise the car. This tuneup was created and mainly used by mechanics on racetracks or similar roadway. It was also obviously a reliable way to test the car's handling under stress as well.

Now we have modern fuel injected vehicles with multigrade synthetic oil. This tuneup per se is not required. However, do you notice that after a high-rev drive, your engine seems to feel silky smooth even at driveway speeds? Why is that? Are we imaging things ? Or could it be the blessings of the Madonna (who is, of course, italian)?

If your engine does not relish and luxuriate in a wot (wide open throttle), high rev run, something is wrong with it. If you are afraid to do this on your vehicle, you need to invest the time and money into it to restore your basic confidence in its capabilities.

Originally Posted by robertobaggio20

Yes Padre I agree. As the OP pointed out later, his driving is all city, in which case 18mpg is a fair number. Usually when MPG figures are quoted, the unspoken assumption is 50/50 driving and if this is not the case, it should be explicitly stated. I believe Steve gets as high as 28 mpg (from a response to one of the first threads I started on the forums) on his vanos E34 but he does alot of highway driving.

Mine's non-vanos and its about 26 now. I need new coils though so I might be able to squeeze 28 out again with new ones. And yes, 80% of my driving is highway.

Originally Posted by BMR_LVR

Mine's non-vanos and its about 26 now. I need new coils though so I might be able to squeeze 28 out again with new ones. And yes, 80% of my driving is highway.

I am not far behind with my 535. Prior to installing the EAT chip I was at a solid 25 mpg avgerage, 80% hwy. Post chip I am at 24 and 27 when all highway. I would like to replace the injectors next, I think there is a bit more left in her

Consider your tire/wheel combo too. Those of us on skinny 15's have an advantage

Hi all,

Baggio is a soccer player famous for is flying feet....and temper

Latin's famous for temper, and I'm included. My 2.5 gets it own decarb on a private driveway and sounds good. Even on 6k rpm run.

But smoke fume may depend on outside temperature. If smoke is with cap on something maybe wrong and I really don't know what's wrong. Can someone point a direction??

Best regards