Chevron Delo 15w40. 15w40's are much more robust oils than 10w40's since they are designed to be compatible with diesel engines so they are very shear stable and have great cleaning detergents. If your using a non-synthetic I would highly recommend a 15w40, Chevron Delo is a good choice and extremely affordable. BMW dealers sell 15w40 also which I would imagine is made by Castrol like their 5w30 (which is a european castrol oil and is truly a blended synthetic, not a full synthetic like BMW states on the bottle and actually near 40 weight). Mobil 1 5w30/10w30 are not BMW approved oil and run on the very thin side of the 30 weight. They are not even LL-01 approved for current BMW's. Mobil 0w40 would be a better choice and is LL-01 approved, which doesn't really even matter for these older engines.
Personally if I was going to run synthetic I would go with a 0w40/5w40. There is no need to run 20w50 as that was recommend back when dino oils were primarily used and BMW wanted to make sure they could rely on one of the thickest oils to withstand the abuse of the Autobahn. Realistically, a 15w40 will still be the better choice as 20w50's have a small market these days so are less developed and not to mention they generally shear down to a 40 weight in time. Spending over 3 years on bobisitheoilguy.com has taken over haha. BTW, in the other BMW's in our family I use Lubro Moly 5w40 (full synthetic) in the `93 325is and Castrol Syntec 0w30 (actually a group IV full synthetic unlike other castrol syntec's and LL-01 approved) for our `02 325iT. |