[Vwdiesel] Rabbit Droppings #38 (Esso AD 100)

[Scott Kair]

Hagar wrote:

    >>AD oil is lube oil for piston aircraft engines. AD stand for Ashless
Dispersant. it is no longer available.<<

    Maybe Loren will remember the specifics better, but a few years ago,
there was an extended discussion of why adding 2-cycle oil to fuel seemed to
improve fuel economy in our 1.6's.  (Usual caveats about my memory apply
from here on.)
    There were some fairly well controlled tests, and we couldn't explain
why it worked.  Eventually someone ran a search on the two-cycle oil
standards, which aren't SAE or API sanctioned, and we discovered that an
additive package designed to reduce ash residue and smoke was added to the
oil.  Further research pinpointed the ash suppressant as the likely cause.
It was some sort of elastomeric polymer whose main use was in roof coatings.
The consensus seemed to be that the stuff bound with fuel and allowed it to
break into smaller drops, which led to improved combustion efficiency and
hence better mileage.
    ESSO- Standard Oil- became Exxon down here several years ago, but I
wouldn't be surprised if the Ashless Dispersant were the same or similar to
the stuff in 2-stroke.
    Scott Kair