IML: The old oil argument

[dardal@xxxxxxxxxxxxxxx]

... with Dick!  ... and some with Paul

Please see inserts

Quoting Dick Benjamin <dickb@xxxxxxxxx>:

> >>>>Straight 30 weight? I usually use 10W30 or 10W40, as per the manual on
> my 

> 10W30 is very thin oil, especially for a car with 35 years of use on it.   I
> use SAE30W in all my old cars, but my choice is somewhat influenced by where
> I live.  Our temps almost never go below 32 degrees, and SAE30W was the
> recommended oil for that environment, even when the cars were new.  A more
> worn engine requires heavier oil to maintain proper oil pressure.  See what
> the factory says about this - - - 

Dick, I am not certain if the SAE 30 was recommended for these temperatures or
simply considered a possible/allowable alternative.  I think its the second. 
The only advantage of the 30W over the 10w30 is that since it does not rely on
the additives for its increased viscosity at higher temperatures, it may last
longer than the 10w30.  But assuming the oil is still "fresh", the 10w30 will
do a better job protecting your engine over the overall driving cycle, there is
no question about that.

> 
> The following is quoted verbatim from the 1972 FSM (the capital letters are
> theirs, not mine!):  "IMPORTANT:  If the vehicle is to be used for maximum
> performance service (very high speed or very rapid acceleration), the engine
> requires heavier than normal lubricating oil.  This is due to the high
> speed, loads, and temperature of moving parts developed in these engines
> during this type of operation. "FOR BEST PROTECTION OF THE ENGINE UNDER
> THESE CONDITIONS, THE HEAVIEST AVAILABLE ENGINE OIL OF SD OR SE QUALITY
> SHOULD BE USED THAT WILL PERMIT SATISFACTORY COLD STARTING. [these are
> obsolete quality ratings, today we would say SJ or SI]  

Absolutely correct, that's why I use 15w50 Mobil 1 in my 440s.  The main reason
for that is the following.  These are 7.2 liter engines with only 5 quarts of
oil (when full, 4 when low).  Most engines of half the displacement have the
same amount of oil.  That means that the oil can get hot real fast when you
drive it hard.  Since oil loses viscosity with increasing temperature, the
higher grade is needed, so it still has acceptable viscosity at the elevated
temperature (the down side is loss of gas mileage at low loads, and that the
engine will not give you its full power potential until the oil is thoroughly
warmed up).  In this respect, the multiwieght will do much better than the
single weight, because its viscosity index (ability to maintain viscosity at
higher temperature) is better, even if it looks thinner at room temperature. 
The Mobil 1 or other synthetics are of course even better since they have even
higher viscosity index and they rely less on the viscosity additives so the
lubricant properties are more consistent with time and miles.

> 
> SAE 30 AND SAE 40 ARE RECOMMENDED [then it goes on to discuss multigrade
> oils, which are also permitted, if 20W40 or 20W50 is used, with a special
> "high performance" additive (STP?). 

Now, even the cheapest multiweights will be far superior than what was available
back then.  They will easily exceed the standards of the best oil of the early
70's.  

> improvers are not lubricants - My understanding of the reason is that they
> are simply thickening agents, so when the lubricant is under great stress
> (high temp, high loads), the coefficient of friction is higher than with
> straight weight oils.  I also have some antique heavy equipment (dozer,
> backhoe, skiploader etc), and those manuals are very emphatic about it.
 
Dick, this is simply not true.  They absolutely are lubricants.  The reason old
heavy equipent was "afraid" of the additives is that they simply did not trust
their longevity.  I do not blame them.  These have been vastly improved in the
modern times.  Now all diesels use 15w40 grade, and will likely go to 10w30 in
the future.

>  
> 
> In my modern cars, I don?t agree with the recommended 5W30 oil either.  I
> believe the car manufacturers specify very thin oil in an attempt to satisfy
> the CAFÉ requirements - they don't give a hoot how long the engines last, as
> long as they go beyond the warranty period. I switch to 10W30 after the 

That's part of the reason.  However, as long as the 5w30 oil is within its drain
interval, it will protect the engine better than the 10w30 because it has higher
viscosity index.  Again, the 10w30 may have higher viscosity at room temperature
than the 5w30, but thats irrelevant.  What counts is its viscosity at over 100
degrees C.
> 
> Enough of my biased opinions - suit yourselves, guys.
> 

We are all biassed to some extend Dick.

Quoting RandalPark@xxxxxxx:

> I use 20W-50 in it. I also use 20w-50 in my '56 Imperial since it is pretty
> tired as well, but I am now thinking of changing that one to SAE40W, since I
> think it is actually heavier.

Paul, the SAE40W is heavier than the 20w50 at ROOM temperature, but not at
engine operating temperature.  You are better off keeping the 20w50, especially
if you drive your car hard.

D^2



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