My understanding is that the "slick" bit is removing $$ from your pocket....
About 12 years ago I was persuaded to become involved in a long term test of an
oil
additive (ptfe type) in my car - a 728i BMW - because I had comprehensive
records
of
fuel and oil use, going back over 20,000 miles. Initial (subjective) impressions
were
favourable: the car idled at +100 rpm and it had to be reset. After a further
12,000
miles with additive, fuel use remained identical, both in terms of band and
total
average (15.7m/impG) and oil consumption increased slightly - as you would
expect
of an
engine getting past its best. In the end, (about a year after the end of the
test)
the
engine died from a cracked head - a common problem with the particular engine.
Conclusion: waste of money....
The synthetic/semi synthetic question is quite clear: full synthetics will not
carry
lead compounds in suspension or solution, so they settle out, potentially
blocking
oil
flow. If you use any avgas, don't use full synthetics.
The only advantage is that full sythetics will continue to function at
abnormally
elevated temperatures - however, semi synthetics are a blend of mineral and full
synthetic oils (despite the admonishment not to mix them - I asked Shell
Aviation
specifically what thier W15/50 comprised of) so you get the best of both worlds.
In practice - from experience of world championship level 24hr motorcycle
endurance
racing (we were the #1 privateers for 9 years) we had no problems with
conventional
oils
- so for engines operating under rather lower levels of stress (eg aircraft
engines!)
I
don't see the need to have an oil with much higher limits when it's never going
to be
required. Better to spend your money on more frequent oil changes - and take
note
of the
oil companies recommendations to change the oil on calender time as well as
hours
in
use.
There is one additive that does work - fact: Triphenyl phosphate, better known
to many
Lycoming users as LW-16702, is an anti-scuff/extreme pressure agent that must be
added
to some types of engines at every oil change (via AD 80-04-03) to protect cam
lobes
and
followers. Its already loaded in the correct proportions in many aviation oils
-
Aeroshell 15W/50 for instance - and it works excellently - however, add too
much,
and it
promotes corrosion, being hygroscopic. This is the gist of the message from the
oil
companies about using additives - know exactly what you are doing, or you might
upset
the balance and do more harm than good.
On a nostalgic note, I remember when the arguement was about monograde vs
multigrades...
The Rotax will get a multigrade, but the Gypsy Major still uses monograde oil
(W80
at
this time of year)
all the best,
Miles
|