MB 229.1 vs 229.3?
 

which is the correct one to use for a 1991 500SL? is mobil 1 15w50 good for this engine or mobil 1 10w30?

If you get an oil with the API rating up around SJ you should be OK. When the car was built it was probably only SF or so, so SJ will work fine, any viscosity you feel is appropriate for the weather.

Gilly

Mobil 1 10w-30 is NEITHER 229.1 or 229.3. Mobil 1 0w-40 & 15w-50 are the only approved Mobil 1 oils for your car. There are other approved oils besides Mobil.

-brian

what is the difference between 229.1 and 229.3? on the back of mobil 1 15w50 it says it meets MB 229.1 and on lubro molly volly synthese 5W40 it says it meets MB 229.3....whats the difference?

They rate 229.3 for longer drain intervals (in newer cars) and slightly improved fuel efficiency (0.5-2%) over 229.1. Its unlikely that you'll see a 15w-50 that's 229.3 or 229.5 Mobil 1 15w-50 works very well and is readily available at a reasonable price. The Lubro Moly 5w-40 is excellent also, but is usually significantly higher priced.

I believe 229.3 is the newer version, for use in 2001 models & up.

Thanks a lot guys, I guess since my car is older I can just use mobil 1 15W50. My mechanic told me that these engines dont run well with lower weights. he says use 20W50 year round.

On the pre-fss cars (before 98 or so) you just have to meet the API service classification. The API classification for a 91 is probably a lower classification than what is current, but it's difficult to find oil that is a lower classification than the current one, unless it's some pretty old oil that's been sitting around.
Again, just use an approprite viscosity for the anticipated temps for the next 3 to 6 months, however long the oil will be in there.

Gilly

where you located? 20W-50 is as thick as you can get. I would stick with Mobil 1 15W-50 for synthetic. For dino oil, use Mobil Delvac 15W-40 or Chevron Delo 400 15W-40. These oils meet the latest standards. Though as Gilly mentioned, the standard of the day when your car was made has since been superceded.

Right. On a pre-FSS car, you are still fine going by the API classification only.

Gilly

Thanks again guys. I live in vancouver BC. The coldest it will ever get here is -10 C, and that might be only for 2 weeks in the year.