Just thought some might find this interesting, from the Piper Owners Society website.
Ron Wrote:
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> You do NOT want to use any automotive engine oils
> in an aircraft engine. The crankshaft and rod
> shell-type bearings in an aircraft engine are made
> from different alloys (containing silver) than an
> auto engine's bearings (no silver), and the
> organic zinc compounds that auto oils are loaded
> with, will attack the aircraft engine's bearings
> and leech out the silver and ruin them. You only
> want to use aircraft oils made for piston aircraft
> engines, and change the oil frequently or it will
> end up costing you a premature engine overhaul.
>
The only place you will find siler bearings is in some radial engine bearings. The sulfur in zinc dialkyldithiophosphate will attack silver and copper however there are inhibitors used to prevent that.
> Aircraft engine oils are contain ashless
> dispersant compounds that help to keep the
> tetraethyl lead combustions by-products (lead
> ash) in suspension in the oil, so they do not
> deposit into thick grey sludge in the nooks anc
> crannies inside the engine. Auto oils do not have
> this additive, since leaded auto gasoline has been
> completely removed from the US market for about a
> quarter of a century now.
There is about 3% polyamine "ashless" dispersant in aviation oils. There is about 5% in car oils and 9% in heavy duty diesel oils. It is the oxidized fuel components (from blow-by) called deposit precursors that that the dispersants bind to. The lead particles get caught in the carbon deposits and add thickness. The lead particles by themselves do not cause any problems.
The major problem with using auto oil is the metallic detergents. The FAA is concerned that aircraft engines burn some oil and that these metals will form metallic oxide hot spots in the combustion chamber. These deposits can cause preignition and serious engine damage.
>
> There are available on the market right now, two
> brands of premium semi-synthetic aircraft piston
> engine oils that are very good, and considered by
> most to the best that money can buy: Aeroshell
> 15W-50 and Exxon Elite 20W-50.
Aeroshell contains about 50% polyalphaolefin (PAO) and Elite contains 26% PAO. I cannot imagine a worse base stock for aviation use the PAO. Mobil AV1 was 100% PAO and had terrible problems with carbon deposits capturing the lead particles.
>
> There used to be a total synthetic aircraft oil on
> the market many years ago, but it was miserable at
> the task of lead ash handling, and many engines
> were ruined by the accumulation of the thick grey
> lead ash sludge in them.
>
> If you are concerned with the expense of frequent
> oil changes, then use Phillips 20W-50 XC
> mineral-based oil. It's much cheaper than those
> premium semi-synthetics, and will keep your
> engine lubed just as good and the engine will last
> just as long. All official aviation piston engine
> oils on the market today are very good oils, as
> long as you change them regularly to keep the
> engine clean inside. The premium semi-synthetics
> are probably a bit better if your engine sits in
> the hangar unflown a lot, as they have an
> anti-corrosion additive that helps reduce
> corrosion in engines that aren't run as
> frequently, but if you do fly frequently (at least
> every week or two), then the cheaper Phillips
> 20W-50 mineral oil is excellent, and the
> thriftiest choice of oil you can buy on the market
> today.
>
> Personally, I run Exxon Elite in my airplane these
> days, because it often sits in the hangar for 3 or
> 4 weeks in between flights, and the extra
> corrosion protection claimed by the manufacturer,
> and also reported by many users, makes me feel
> more comfortable, but back in the days when I was
> flying every week, I used Phillips to save money.
> My engine now has 1700 hours on it (it's an O-320)
> and compressions are still in the 70's and it runs
> great, does not burn or leak any oil, and I have
> no doubt it will easily make it to full 2000 hours
> TBO or beyond, mostly because I took good care of
> it and always changed my oil and filter on
> schedule or even earlier when it started looking
> "dirty" on the dipstick
I was the director of the engine laboratory and Exxon Research.
I performed the initial research on the Exxon Elite. Exxon ended copying the Aeroshell product for business reasons. I was disappointed in the Elite so when I left Exxon I created Camguard. It has 25 times the rust inhibitor that the Elite has, a deposit control package, and a vastly superior antiwear package.
Regards,
Ed
Edward Kollin
Technical Director
Aircraft Specialties Lubricants
http://www.aslcamguard.com |
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