What Weight of Mobil 1 Should I Use?

Mobil-1
Syntheric oil is made is 4 weights:
0W-30
0W-40 (not commonly
available in the U.S.)
5W-30
10W-30
15W-50
Here is some
information to help you decide which one to use.
Warranty: The
Owner’s Manual tells what oil Chevrolet wants you to use, and ignoring
their specs COULD result in engine damage. Worse, it COULD result in
denial of warranty coverage for engine damage. For 2001, the required oil
must meet GM spec 4718M. Mobil-1 0W-30, 5W-30, and 10W-30 all meet that
spec. I don’t have samples of the other weights, and so I don’t
know if they meet the spec.
The 2001 Owner’s Manual also recommends
5W-30 at all temps, although 10W-30 is acceptable for temps above
0’F.
Viscosity: I was able to get a copy of the Mobil-1
viscosity/temperature chart from 300’F (150’C) down to -40’F
(-40’C) for all weights except 0W-40. As you would expect, 15W-50 is
significantly thicker at all temps. Aside from the warranty issue, I
would not use it unless my engine was very loose and/or running at
extremely high temps.
Two things stand out on the graph: First, the
viscosity of Mobil-1 0W-30 and 5W-30, within the temp range mentioned, are
virtually identical: the two lines on the graph just look like one thick
line!
Second, the all three weights (0W-, 5W-, 10W- ) are almost
identical at 300’F. Of course, the 10W-30 is thicker at lower
temps.
Other issues: The closer together the two numbers in the
weight, the more resistant the oil (usually) to some types of breaking
down. Since the 0, 5, and 10 are about equal at high temps, we should
chose the one that is most appropriate for our COLD temp starting
lubrication.
Doggone it, I think Chevy got it ABOUT right. Personally, I will try
to use 10W-30 if my coldest starting temp is above freezing. For those
times of the year when starting temps are likely to be below freezing,
I’ll use 5W-30.
You might wonder why they even bother to make the
0W-30. A Mobil engineer told me that at temperatures colder than -40’,
the 0W does have some advantage. Most of us avoid that part of the
world.
Other brands of synthetics may be better or worse but I have
no information to make comparisons.
I hope this info is
interesting, and helps you make a good choice for your oil. Enjoy!