hey there ,
first of all sorry for my bad English ,

i just bought a 535i 2007 a month ago the first thing i did is changing the oil so i changed it with 7 quarts of RAVENOL 10w40 , the problem is the car needs 1 quart of oil in every week or 10 days depending on how i drive it so far i added 3 quarts of oil in the last month , friends suggested to change the oil to 20w50 they said it will be better for the car and the oil evaporation will stop ,

thanks guys in advance

 

and btw there is no smoke coming out from the exhaust .

 

Higher viscosity oil in this engine would be a bad idea - with 10W40 you're already thicker than the 5W30 specified. If it's losing oil, find why first. Leaks can be masked for a long time due to the underbody paneling and the structural panel under the engine. How many kilometers on it? Mine loses 1L in about 5000km at close to 200,000km on the clock.