<VV> Multi-grade vs. 'straight weight' evolution of oil ...

[Charles Lee]

Jerry and Bob, et alia ~

With all the talk a while back about multi-grade oil being so good now, and
all of the misinformation that caused Corvairs problems back then (tire
pressure bias, etc), I thought I had been misinformed 'back in the day' and
was a victim of the rumor mill in regard to oil.

I try to read all that goes on in here, and even between the lines, so to
speak, but I guess I missed the original thread ?

Thanks to all for a very informative debate, setting things straight in my
mind, at least.

Now if I can just get her running, so I can put it all into practice ;>}) !

Thanks to all 
Charlie

-----Original Message-----
From: virtualvairs-bounces at corvair.org
[mailto:virtualvairs-bounces at corvair.org] On Behalf Of vairjer at comcast.net
Sent: Wednesday, November 02, 2011 5:38 AM
To: Post VirtualVairs
Subject: Re: <VV> Multi-grade vs. 'straight weight


Charles, et al... it is true that the manuals specified multi-weight oils
during the 60's, BUT> 

The actual fact of the matter is not so much urban legend as that GM did not
go "public" with the fact that testing of certain brands revealed that some
multi-weight oils had serious problems with "shearing" of the long chain
polymers that made the often used 7W base oil into the 10W30 would result in
a basically 7W oil after as little as 1000 miles. Internal memos and some
service bulletins issued in the middle of the 60's recommended NOT using
certain brands of multi-grade oils in any GM engine whether air cooled or
not....GM did not want to go public and end up in litigation with certain
oil companies, but worked privately to provide their information and
guidance to those oil companies. Eventually, the problems with the polymers
used were solved and "shear stable" multi-grade oils were available across
almost all brands of oils. In the mean time, enough "leakage" of information
reached the general public to make many folks aware of the potential of oil
breakdown but limit
 ed knowledge about which brands to avoid. 


As a "Reliability" engineer at Delco Remy during the 1965-1967 time frame I
read a few reports from the tech center describing the problems encountered
and the recommendations for oil use in "company cars" in our fleet. 


So, straight weight oils were not as weather friendly, but they were
"Stable"....eventually all mult-grade oils became far superior once the
process to assure stable polymers was well known. 




Jerry McKenzie 
PCCA 
Springfield, IL
 _______________________________________________


From: hallgrenn at aol.com [mailto:hallgrenn at aol.com] 
Sent: Wednesday, November 02, 2011 4:43 AM
To: chaz at properproper.com
Subject: Re: <VV> Corvair Tall Tales ~ Is 'straight weight' oil better ?

Charlie,
 
For what it's worth, I agree that today's multigrades are much better.  In
the '70s GM even specifically recommended against using 10W 40 oils in its
engines because of break down (10W 30 was OK).  The long chain polymers that
keep the low viscosity base oil (the 10 weight base) as thick as 40 weight
oil at operating temperatures broke down rapidly due to the shear forces in
the engine.  After a few thousand miles it was no longer 40 weight at
operating temps.  Based on the reports I read in the '70s I stuck to
straight weight oils (even using 40 weight racing Quaker State on summer
trips to South Carolina).  But all of my Corvairs use a multiweight
synthetic now (I used "high mileage" oils for the extra zinc compounds and
add some zince supplement).
 
Bob