Oil smell in car

[M535i]

I'm getting a oil burning smell that's a gassy oil smell in my 535i at red lights but only sometimes and in drive through a but only sometimes and it's a harsh nasty smell that doesn't linger but disappears rather quickly. The valve cover I know is a common leak but I can't find leaking oil anywhere and not losing oil, I lost about quarter quart the last 3,000 miles. I was running mhd e30 tune which is when I'd get the occasional harsh oil/gassy smell so i filled up with shell 93 and went to 93 1+ tune and had no smell for about 300 miles so I flashed e30 back to the car filled up with e35 and the oil/gassy smell came back occasionally at lights and drive through but when I got fuel I went to shell 93 and flashed 1+ and no smell the whole tank and have stuck with the 93 tune. What could possibly cause the oil/gas smell only when running e30?

 

[NoQuarter]

Do you have cats or catless?

 

[M535i]

Yes I've got cats, 65,000 on engine

 

[Milan]

There is no way you can see if the back of the valve cover is leaking in a 535i. If you don’t know when it’s been changed it’s probably leaking.

Could be turbos too

 

[doublespaces]

Do you have a catch can or anything which vents to the atmosphere?

 

[NoQuarter]

Probably valve cover leak dripping onto cats. Dont need enough dripping to notice any oil lose.