There is little correlation between car engines and most aircraft engines.
The problem with car engines is acid build up caused by low oil temps not
boiling off the condensate during each use. The water combines with the sulphur
compounds from combustion and forming sulfuric acid among a witches
brew of chemicals that are not associated with lubrication. The oil in the
bottle or can comes with several chemicals that will neutralize some volume of
acid. Once it does that, additional acid is free to do the bad mojo on the light
alloys in the engine. Channels in the bearing faces. Blackend stripes around
edges of bearings, rough surfaces on normally smooth die castings and so on. It
is seldom that a car sits idle for more than a week.
It is the reverse for aircraft. A month off is not uncommon. The rotary
with its hotter oil soon after startup has no problem boiling off water based
products. It has minimal crankcase volume and on cool down sucks in only a small
volume of humidified air, so less condensate than a piston aircraft engine. You
should put a filter on your breather, because it does suck air into itself
on cool down.
I have been gifted cars owned by girls that have never had the oil changed.
Of course the engines were seized. The breath of Cesar problem. (Evidence of the
first oil will always be there)
The object of changing the oil, is to dispose of the acid and renew the
anti acid package in the oil. At the same time the other products of
combustion that have slipped by the seals are removed as well. But the hot oil
of the rotary is a big help so long as it runs long enough to get the oil hot.
If you have a screw together filter housing in the drain from the reduction box
containing a magnet to stop any steel being dropped off the gears, (no element,
just the magnet) then an annual oil change sounds perfectly acceptable. The
engine is under no strain at all and specialty oils are of little value. Use
whatever is best for the gear box. A car racing oil for its extra anti acid
package and extra zink anti scuff compounds would be better. And a separate oil
supply for the rotors of 2 cycle oil would keep the housings clean and the seals
free in their grooves.
If you use the Oil metering pump, the crank case oil will be dropped into
the rotor housings. Regular street oil resists burning and leaves behind
unburned crap from the multi grade plastics, in the housings, fouling the apex
seals. If you use the OMP, stick to straight wt. oils. Racing oils make it worse
as they resist burning or even breakdown to higher temps. Synthetics don't burn
at all and are a bad choice for OMP use. You can leave the OMP on and
cut into the passage in the front cover anywhere its handy and install a dash 3
fitting and run 2 cycle oil from a bottle on the fire wall. Plug the oil passage
at the face where it connects with the front iron. Now you can run any
crank case oil and not worry about the apex seals.
I used Redline synthetic 40 wt. racing oil in the crank case of the race
car. The top oil was Redline synthetic racing 2 cycle oil (for dirt bikes) and
never a failure. No wear on apex seals (soft carbon). I changed oil every 4
races, about 8 hours or a bit less. The pretty green oil (not red?) would
be black after 4 weekends. Engine was used between 7,500 and 9,600 RPM. Oil
pressure is 100 pounds. oil temp is 180 to 190 (hot day) and water 160 -180-
(hot day) If we could not get to 160 we put the thermostat in it.
Lynn E. Hanover
So 15K at an average of 150 MPH would be 100 hrs…Most
cars change at 3K to 7K I think…7.5K would get you about 50
hours..??
There is no stop and go to build up water and
stuff. I bet you could get 100 hours on 12 quarts of Mobil 1 with no
adverse effects.
What do you think, Lynn?
Bill
B