BMW E92 330i gas smell in oil

[SelmirDE]

Hallo guys,
When I open oil cap I can smell gasoline. I changed oil 1000 km ago. I know it can be lot of things but where should I start. Car starts good and have no power loss. I know this is not pofesional tool but got checked on Thorque app for missfires on 30km run it had 2 missfires on 3. and 4 missfires on 4. cylinder that was 1 hour trip. Car had for cca 1500km all coils and spark plugs changed.

[SelmirDE]

Does anyone have idea what could it be?

[RocketSurgeon]

Usually gas in the oil is a complaint on DFI engines. On your car, It could be a stuck injector leaking fuel, or something related to that misfire. If you have a sketchy coil occasionally not firing, that unburned fuel could run down the cylinder walls and contaminate the oil.

[slides]

if you do a lot of short distance driving that can contribute to the fuel in oil.

[SelmirDE]

Forgot to say and mine oil was just after 500km black.

[NeedForBoost]

Selmir, I am not very experienced with the n52/n54 engines as they are new to me but as pointed out by Rocket, the gas smell can be caused by an injector malfunctioning or can be an inherant problem with DFI engines. However I have experienced oil that gets very black and dirty in a very short time, this is a more serious problem in my experience. I have run into this on a few different motors. As you probably know, the 'dirty oil' is caused by combustion gases/products getting 'past the rings' so to speak. The piston ring's job is to keep the combustion process 'at the top' between the piston and the cylinder head and valves. If there is a sealing problem and the gases can escape past the rings down the cylinder walls and into the bottom end of the motor where the crankshaft and oil live. Depending on how serious the leak is, the oil can get dirty very fast. I have one motor now in an older collector type car thatr has a cracked ring land, that's the area of the piston that holds the ring land. I already know I need to replace at least one piston but since I want to get a couple other motor projects done first I am just running VERY thick oil (basically two liters of oil treatments (I use Lucas treatment, it's probably about 70-90 weight thickness) per change of oil. I am also changing the oil every 500 o so miles, this keeps the smoke from the damaged ringland to a minimum when diving the car.

The other time I've experienced oil getting contaminated quickly was on a new rebuilt motor with new pistons and rings and a freshly honed block. For whatever reason, the rings did not 'seat' or seal up properly during break in. Obviously not the issue with your car.

So my recommendation would be to have a shop perform a "leak down test" on the cylinders, it shouldn't be more than 1.5-2 hours of labor. It's basically pressurizing the combustion chambers and measuring how much of that pressure is sneaking past the rings(or valves). It's a diagnostic test and not the cure for your problem but it will help guide you to the next step.

[SelmirDE]

Thank You for Your answer. I will let them do compression and leakdown test. I tested already injectors and 4 of them was leaking. So I am about to order all 6 of them. One question. Can oil get black fast when injectors are not good? I mean when gas dont burn as it should be sould it make more soot or so? Mine exhaust pipes are really sooty after few days after I clean them. I dont see that car smoke maybe a little bit at night when someone drive with xenon behind me.

- - - Updated - - -

Forgot to say only at night when someone is behind me and full throtle.

[NeedForBoost]

In my opinion no, the leaky injectors would not cause the dirty oil, gas smell yes but dirty oil is caused by contamination from combustion products. It happens normally over thousands of miles but if it is happening so fast as 500Km, you have a separate issue. Do the leakdown test.

[SelmirDE]

Thank You for Your answer. I will do it.

[testify]

Do you always warm up your car before driving? Do you let it idle a lot?

During the aforementioned activities the rings on the pistons don't seal well from being cold, and from lack of load and therefore a lack of pressure in the combustion chamber to get the rings to make a tight seal against the cylinder wall.

This results in gas blowing by the rings and into the oil. I always avoid idling and long warm ups for this reason.

[SelmirDE]

I always wait to rpm drops to 650rpm (15-20 seconds not sure) and dive it away. But when my wife drive it its not like that. She need time for some other stuff before start driving. hehe