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

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Paul-regarding the pros and con's of adding oil to wing tanks, that is what
we did with the RV-4 from 1988 to almost 1998 with two different prototype
rotary engines of varying configuration. Ditto the RV-3 which Alan flew with
our Mk II Superlight engine for five years from from 91-96 and the Mazda
conversion engine in 96& 97.  Often there were extended down times for both
aircraft at different times. In all those years we never had any operational
problems related to mixing oil with fuel in the wing tanks.

At first we assidiously mixed the oil with fuel when refueling but as time
went by, simply poured in the oil when fueling.  At one point the RV-4 was
sitting for over a year when a new engine was being produced.  We didn't
even periodically rock the wings when it sat in the hangar then or any other
for prolonged periods.

We never experienced a problem except when the driver was tired, lazy or
both flying from Little Rock, Oshkosh or some other such long haul to Oregon
in one day.  On those hot summer days or on other multi-state hauls, I
bitched about having to futz around with pulling the oil out of the baggage
compartment, dip the tanks to determine the correct amount of oil  for each;
decant the correct amount of oil for each then put everything away.  It was
not normally a big deal unless it was 105 degrees under a hot sun and trying
to keep the refueling stop time to a minimum.  Everett always maintained
completely tongue-in-cheek that it wasn't a problem for him (he would drive
the air conditioned motorhome to the destination airport of Oshkosh,
Lakeland, Arlington, etc. so we had a nice handy HQ and bunk).  The
convienence factor appears to be the one major argument in favor of some
type of metering pump and remote tank.  That is, unless, you forget to fill
up the oil tank and don't have a warning light or other device that reminds
the knothead behind the stick. But again, a metering pump, tank, lines, etc.
simply adds to the weight, complexity and failure modes of the installation.

Steve Beckham

Something for everyone to consider. On the last of the Kawasaki road-going
two strokes they injected oil directly into the carb float bowl. Earlier
they had it going to the carb inlets. Point being the thought was that mixed
into the fuel was best. Once synthetic oil was available we took the
throttle cable off the pure and ran on revs alone. Very lean mixtures were
OK. They never stopped changing the oil injection set up.
Lastly, they never ran oil injection on ANY roadracer. ALWAYS ran pre-mix.
On your plane just record the gallons from the pump into each tank. That is
plenty accurate for the mix.
Bill Jepson



Paul, no reason for the battery to go dead in a couple of weeks. Check the
battery to see if it alone is weak. And we have had several RX8's in with
dead batteries that had the trunk lid popped. The trunk wont open enough to
tell its open, but it turns on the trunk light. It takes about 3 days to
kill the battery. You might check that.

Bob Mears

Thanks Bob, I'll check the light switch and make sure it is working.
Come to think of it the auto side door opens on my Honda Odyssey sometimes
just putting the  key Fob in my pocket.

Paul Lamar