oil grades

[tedcrum@xxxxxxxxxxxxxxxxxxxxx]

15w-40 petroleum oil is the right viscosity for your car. Most synthetics
suitable for the same service would have a rating of 5w-40, since you take
advantage of the better vi at the low end. BMW's own synthetic oil is, in
fact, 5w-40.

There is no 5w-40 rated oil in the Mobil 1 automobile line, though they
make the truck oil Delvac 1 in 5w-40 (which I intend to use at my
next change, I am also using 15-40 petro oil now). Mobil 1 15w-50 is to
thick; BMW recommended Mobil 1 10w-30 by name in a service bulletin before
they introduced their own oil. The Mobil 1 10w-30 is really more like a
10w-40, but they rate it that way to match the owner's manuals of US cars
which warn against 10w-40 because some of the earlier petro oils coked.

- -Ted Crum
 1988 735i 5-speed
 tedcrum@domain.elided


>>>>>>>>>>>>>>>>>>>>>>in response to>>>>>>>>>>>>>>>>>>
Date: Sat, 29 Jul 2000 17:04:34 -0700
From: Jason M Surprise <jmsurpri@domain.elided>
Subject: 10w-30 or 15w-40?

Kinda confused.  The owners manual for my 94 325i shows 10w-30 is
suitable for -20 through 40deg (f) ambient air temps while 15w-40 shows
0 through 83deg.  Looking at past dealer receipts, it looks like they've
always put in 15w-40.  I'm switching to synthetic and doing my own oil
change this time.  I am inclined to stay with 15w-40, however I was
always under the impression that 10w-30 was the way to go from posts
I've seen on here and other places.  It just seems counter-intuitive
since average temperature around here doesn't get anywhere near that
low.  Are there any risks of running 10w-30?  Does one offer a better
performance advantage over the other?  I'll be putting in Mobil1 if that
makes any difference..

Thanks!
Jason
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