🚀 go-pugleaf

> Hello!
> 
> I have used only 20W-50 oil for the past ten years or so.  According to my
> Toyota owner's manuals, this is good protection down to 10F.  And it sure
> makes me *feel* more comfortable on really hot days in the summer.
> 
> If the tradeoff is thick oil & better protection versus thin oil & better
> gas mileage, I would choose the better protection.  
> 
> So what does everyone think?  Nowadays, 15W-50 is available.  Would that be
> perfect?
HISTORY OF MOTOR OIL 
Quoted from RIDERANNUAL - 1984
"Back in the 1930's, Society of Automotive Engineers (SAE) developed service
classifications for engine oils. The first were SA and SB. SA is for
utility motors such as generators operating under low stress
conditions. This classification has no performance requirements.
An SA oil may have no additives at all, or it may contain pour and
foam depressants, to preventthe oil from frothing inside the engine.
SB is now described as a minimum duty oil for engines operating  under
such mild conditions that very little protection is required. SB oils
provide only anti-scuff capability and resistance to oxidation and bearing
corrosion. This is the kind of oil you might pour in your lawnmower
today, but could never imagine putting in your car, let alone a motorcycle.
Yet for three decades this type of oil was "the" standard motor oil.

It was not until 1964 that SAE developed a superior oil classification
:SC. Oils with this designation contain additives that help control 
high and low temperature deposits, wear, rust and corrosion. Oils meeting
the SC standards were a significant step towards increasing the 
life of engines and meeting the needs of the powerful passenger car
motors that were being produced during the heyday of the muscle cars.

But they were not good enough. Just four years later, even tougher 
classification had to be developed: SD. These oils provided yet
stronger protection against high and low temperature engine deposits,
wear, rust and corrosion. 
The new classification should have been enough to last
another 30 years. But Detroit makers began requiring
stiffer oil abilities by 1971. Small cars were coming out of the
factory doors in large numbers - Ford's Pinto and Chevy's Vega
showed up around then. In addition more and more foreign cars
with higher revving, small engines were appearing on our shores.

These machines demanded a lot from an oil. So in 1972, the SAE
came up with what they figured had to be the oil category to end
all oil categories - SE. 
It provided yet more protection against oxidation
high-temperature engine deposits, rust and corrosion. SE was the top oil
classification during the 70's, but in 1980,it was replaced by the latest
classification - SF.  This oil provides even more protection - particularly
against oxidation and wear.

The "S" in these classifications stand for spark ignition - ie. gasoline
engines. Classifications that start with "C" specify oils for diesel 
engines(C for compression ignition)."

OIL VISCOSITY
The numbers after the service classification refer to the viscosity of the
oil which is a measure of its resistance to flow at certain temperatures.
The numbers also give you an idea how thin the oil gets when it gets hot
and how thick a layer of protecting  slipperyness will
stay
between the moving metal parts in the engine. The "W" rating, accompanied
by a lower number placed before it, is a measure of the flow rate 
at 0 degrees F. However this rating tells you more than just winter-time
performance.  It  - more importantly - is a measure of its "startability"
or how quickly it will flow to needed areas when the engine first cranks
over. A low number before the "W" is not a bad idea anytime you
care about limiting engine wear.

GM OIL RECOMMENDATIONS
I own a 1984 Chevy Celebrity with a 2.5L 4 cylinder engine. The recommendations
for oil suggest 5W-30, SF classifications with 10W-30 as a second choice. 
I take these recommedations seriously and have found that Valvoline 
produces a 5W - 30 oil that can sometimes be purchased on sale.   

10W-40 weight oil is specifically *NOT RECOMMENDED* according to the 
owners manual and to several mechanics I have querried on the subject.
They seem to feel that the ability to quickly flow and protect
camshaft bearings during startup is the reason for the recommendation.

Hope this helps .
                                          Pete Call




> 
> --
> --bruce
> -- 
> 
> ________________________________________________________________________
> Bruce M. Reynolds              {decvax,ihnp4}!uw-beaver!--\
> John Fluke Mfg. Co., Inc.                 {sun,allegra}!---> fluke!bruce
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