RB wrote:
dpb wrote:
RB wrote:
...

Briggs is not going to spec anything other than regular oil.
...

But the intended point is (which my other response didn't do well)
that they _could_ have spec'ed a more stringent API classification but
didn't. It's not that there's any shortage of grades from which to
choose to meet the needs of the engines they're designing.

That they didn't indicates something...

My points were two:

Air-cooled engines can have localized hotspots that exceed the temps
found in automotive watercooled engines. Speaking only of areas touched
by the oil.

"Can", yes. Smaller and less performance driven engines less likely.
I'd also wager quite a bit that the engine manufacturers look at
temperature distributions quite a bit in the design process.

Current API specs have all but eliminated the traditional, and most
effective wear reducing additives so as not to foul your cat convertor.
To get the wear inhibitors back, you have to look at oils made for
engines without catalysts - race cars, motorcycles.

That doesn't mean that there aren't different than the traditional wear
additives currently in those oils. There are some very smart folks
doing lubrication design these days w/ far more sophisticated chemical
modeling tools, etc., than in those days of yore.

Will small engines last a long time using motor oils formulated tot he
current API spec?
Undoubtedly.

Are they ideal for the application?
No, they are designed to a different operating environment.

Is the engine manufacturers branded oil the best for their engines?
Not necessarily.

OTOH, is some other selected ad hoc oil any better? Not necessarily.

The primary disagreement I have is the conclusion drawn that OEMs simply
more or less randomly select something in making those recommendations
and that there is something somehow wrong w/ newer oils simply because
they don't necessarily use the older formulations.

Again, specialty applications are something different than the ordinary
small 4-cycle.

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