[Amc-list] Weighing in on Oil Weights

["Bruce Hevner" <scramblr@xxxxxxxxxxx>]

>I have a 401 Spirit drag car which does see some street time, and I run
15W-50 Mobil 1. Recently I gave a ride to >a friend who happens to be an
experienced AMC V-8 builder, someone whose judgement I thoroughly trust.
He >saw my oil pressure and said to change to 10W-40 (he thought it was
too high). It never goes below 40 PSI >(mechanical gauge). I have the
Milodon sump with external lines to the oil pump. I plan to switch to
diesel 15W->40, both reducing the viscosity and getting the additives
only found in diesel oil now. Comments?
 
I don't think you are going wrong using 15-50 Mobil1 but you're friend
may be right in trying a lighter weight.
 According to the Shell engineers at the PRI show you should run the
LIGHTEST weight you can that prevents bearing and piston problems. How
do you tell?? Keep reducing the weight one step at a time until you
begin experiencing bearing flaking or piston scuffing. Then jump back
one weight.
 Since MOST of us don't have the resources to do that CALL THE OIL
COMPANY and ask them.
 He said currently MOST of the top NASCAR teams are running very light
weight, and have experimented with oil as low as ZERO weight! He
cautioned that bearing clearances must be VERY tightly controlled to run
that light a weight and that realistically there is little gain once you
reach 20wt. 
If you have a roller motor you don't need the extra ZDDP found in the
"high zinc" oil. If you run a flat tappet cam use oil without the
"certified" circle on the label. These oils contain a higher (varies by
mfg) amount of ZDDP to help protect against cam wear.

The reason "racing" oils contain less detergent is those type additives
tend to encourage "foaming" which is NOT a good thing!! One of the
reasons race oil should be changed more often than "street" oil.

As a side note ALL the engineers at the seminar were ADAMANT against
using ANY type of additive other than for break in purposes.

Just passin it on as I heard it,,,
Bruce Hevner  
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