In  eleven years of editing the newsletter nobody has complained about
the
oil  settling
out of the fuel. There are a couple of reasons for this. When you  start
the engine
the fuel pickup in the tanks is at the lowest level  generally so you
might
get
an oil rich mixture (as I recall oil floats on  the top of the fuel) but
that is soon
returned to the tank by the fuel  pressure regulator recirculating the
fuel. At idle it
recirculates as much  as 90% of the fuel flowing through the  pump.

Paul Lamar


The real question would probably be best answered by those engineers
closely associated with 2 cycle oil and it's miscibility with aviation
or other
fuel.

Oil either mixes with fuel and stays suspended (dissolved for want of a
better word) or floats or sinks. It really can't do all three things.
It is
possible that it falls out of solution and then either one of the
other two
is  possible.  (If my limited knowledge of physics is still in tact.)
If it
floats, it will not collect at the lowest part of the tank (the sump)
yielding  an oil rich mixture. If it sinks it will not float on top of
the fuel
(unless  the various densities of hydrocarbons dissociate with each
other and
based on  their  density relative to water they either float or sink.

It might be an idea to, during your preflight, to vigorously shake the
wings for two purposes. 1, to mix the oil, 2 to check the continuity
of the
spar.

Just a suggestion.

Rich

I have just tried this, 5 ml 2-stroke oil in 500 ml auto gasoline in a
glass jar. The oil goes to the bottom. Part does dissolve quickly but
the bottom half of the jar has all the color. The bottommost layer has
the darkest color. It takes some shaking to get a uniform color. If not
shaken, you will get a very oil-rich mix on starting.

Al Rees

That is interesting Al. Thanks for doing that. Let it sit for a week and see if it settles out on the bottom again.

If the pump is pumping 20 gallons an hour
and 90% is recirculated on start up and there is 1 oz per gallon in a 30 gallon
tank that means there will be 30 oz in the bottom of the tank. Or.234 gallon
of oil. 18 gallons per hour divided by 60 is .300 gallons per minute. The oil will
be sucked up in less than a minute and squirted back into the top of the tank.

Check my arithmetic.

Paul Lamar