HMalloy086068

Changed engine oil and filter today on my wifes CLK350 and used Mobil 1 Extended Performance 5w-30 instead of the Mobil 1 European formula 0w-40. Is there any cause for concern or are the two oils similar enough that I can leave it in for the recommended interval? We only drive about 6000miles a year on the car so oil is changed by time. Thanks

Fatz

I am not sure, but would bet that the "extended performance" oil is not a "full synthetic" oil. The "extended performance" will break down differently and leave more "sludge" (primarily due to the temperature range additives and the dino portion of the mix). But I don't think this will be an issue over one oil change cycle.

If you drive aggressively, you should probably change to the full synthetic after 3-4 K miles. If you drive "normally", I think you will be ok to go 5-6 K miles before changing back to the full synthetic Euro formula.

BTW - it does not have to be 0-40. 5-30 (full synthetic) will be ok unless you live in a really cold place and the car is not garaged.

Yidney

Why did you use the "wrong" oil? The viscosity does not matter so much as that it meets the MB spec 229.5. It will say on the bottle.

mis3

MB has been using 5w40 for a while. However, I still stick with 0w40. Regardless, it has to meet MB specs.

Maybe you can change it out after 2-3 months ( low mileage).

Fatz

You're right on the viscosity. My "5-30" was a mistake..... I intended 5-40. The viscosity of 40 will make a difference, particularly for the "speed demons" out there........ (guilty)