Motors oils

[JohnHuntD@domain.elided]

I've owned motorcycles for over 40 years, and motor oils are a frequent topic 
on motorcycle-related web sites since motorcycle engines are generally more 
highly stressed that most car engines.

Like many long-time motorcyclists who do their own maintenance, I've tried 
mineral-based oils, full synthetics, and synthetic-mineral blends. My 
experience reflects the general consensus of motorcyclists on motor oils:

1) I have never had, nor have I ever met a person who had, an engine failure 
in either a car or a motorcycle attributable to the motor oil as long as the 
oil was changed regularly and in sufficient quantity. I won't say that "oil 
is oil" and it makes no difference as long as it is clean and in sufficient 
quantity, but in real-world non-racing use, in anything under 100,000 miles 
and/or laboratory conditions I think the advantages of synthetics vs. 
mineral-based oils are marginal in terms of really making a meaningful 
difference.

2) Synthetics and synthetic blends generally hold up longer without breaking 
down than mineral-based oils, such that 7,500-15,000 miles is now an 
acceptable oil change interval for certain newer cars coming from the factory 
with synthetic oils. (If you disagree, please take it up with the BMW and 
Audi factory engineers who recommend that for my 540i and my wife's Audi A6.) 
Mineral-based oils general break down and their lubricating propoerties are 
diminished long before that. 

However, since good quality mineral-based oils can typically be bought for 
around $1.50 a quart, or 1/4 to 1/3rd the price of a quart of full synthetic, 
it's cost effective to use mineral base oils and change oil more often than 
using the higher-priced synthetics. And for older engines that typically 
suffer more oil contamination from piston ring blowby, changing the oil more 
frequently is a good thing to minimize acids and other contaminants in the 
crankcase

3) On a recent Baltimore-to-Death Valley motorcycle trip I switched to a 
synthetic oil since my understanding is that synthetics maintain their lubric
ating properties at extreme high oil temperatures better than mineral-base 
oils. Within 500 miles I was having oil leaks and oil seepage around seals 
and gaskets that I never had before (see below).

4) Synthetics generally have higher detergent properties than mineral-based 
oils, and I suspect you've seen the ads where an engine after 100,000 miles 
with synthetic oil has much less sludge than an engine with 100,000 miles 
with mineral-based oil. The flip side of that, and verified by every 
motorcyclist I know who has switched to synthetics, is with synthetic oil I 
have oil leaks and oil seepage that I didn't have with mineral-based oil, and 
those leaks and seepage went away when I switched based to a mnieral-based 
oil.

My summary conclusion is that if you have a C5 Corvette, BMW, Mercedes, 
Porsche, or any other car than specifies synthetic oil, you should follow the 
factory engineers' recommendations and stick with synthetics. But for older 
cars, spending $4-8 a quart for synthetics may make you feel better, but in 
my experience provides little real-world benefit over a mineral-based oil in 
normal day-to-day driving. Maybe there's a tangible benefit if you're going 
to take it to the track or drive the car several hundred thousand, but less 
than that, I'm not sure it justifies the price of synthetics.

BTW, my understanding is that Pennzoil has sold all of its refining 
facilities, and is now strictly a packager and marketer of motor oil they buy 
from other oil refiners.

One man's opinion.

John Doak in Baltimore, MD

2002 Audi A6
1999 BMW 540i
1974 Alfa GTV
1949 Chevy pickup
1998 Honda Super Hawk 996
1981 Honda CBX
1952 Triumph 650T Thunderbird    
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