Aviation grade engine oil for genset? - Steel Soldiers::Military Vehicles Supersite

cranetruck · 04-05-2009, 15:27

Opinions, pls, found this:

" Automotive oil should never be used in an airplane engine.
The most important reason not to use automotive oil in an aircraft engine is the number of additives in it that are designed for use in water-cooled engines operating within a certain range of temperatures and pressures and at constantly changing levels of power. Aircraft engines are air-cooled and operate under an entirely different set of parameters."

Genset engines are air cooled and similar to aircraft engines in operating conditions.

dittle · 04-05-2009, 16:48

Bjorn,

I was looking for some oil with a similiar scenario and what I came up with for my scenario is that the materials the seals were made out of have a fire resistance property in them that if you use the incorrect oil reduces these properties. Not exactly answering your question but it is something I ran into myself.

EZFEED · 04-05-2009, 20:56

This would be something I would be concerned about

Any more info?

datsunaholic · 04-06-2009, 02:53

Now, the aircraft engines I work on are water cooled.

The oil we run is around 80 weight, but is formulated for these engines. The issue is the bearing materials- lots of brass bearings/bushings (especially in the supercharger gear train and the cam bearings) and the main/rod bearings are all silver bearings (coated, but it's a microscopic flash babbit coat). Automotive oils would eat the bearings to death, and it's not like these bearings can be found anywhere.

Of course I wouldn't think of trying to run this syrup-thick goop in a car, or a diesel. It has no detergents whatsoever, and has a lifespan of less than 10 hours. Goes in amber and comes out black.

cranetruck · 04-06-2009, 07:52

Water cooled aircraft engines, learn something every day....

chris837rj · 04-06-2009, 13:44

The reason you can't run automotive oil in aircraft engines is because auto oil is not designed to hold tetraethyl lead lead in suspension that is added to 100LL fuel. If you do add auto oil the lead will "fall out" and soon clog up oil passage ports thus causing an engine failure and resulting in a rebuild. That is if you land the plane without crashing...

Speddmon · 04-06-2009, 13:46

I called Onan this morning and asked about oil for the air cooled generator engines and the parts guy told me to use 15w-40. I am going to call back though after I am able to pick up my sets and give then the engine serial numbers and see what kind of documentation (maybe parts manuals directly from Onan) I can get. And I'm going to ask about the oil yet again so they can look up the original recommendations.

M543A2 · 04-06-2009, 15:28

My 4A032 manual says to use OE/HDO 30 oil for temps above 32 degrees F. I assume, correct me if wrong, that means Oil, Engine, High Detergent Oil, 30 weight. I also have military oil information that says for operation from +5 degrees F multigrade 15W40 can be used in lieu of OE/HDO 30. We are running 10W30 Rotella in our 4A032. Others can tell me their experiences with these motors.
I am confused with several statements made in other posts. For one, automotive oil not working for aircraft engines. I understand the differences in air cooled and water cooled, but the part about it eating brass bothers me. We have brass bearings on the distributor shaft and oil pumps and brass valve guides in many engines we own. There has never been a problem with them. Also confusing is the statement about suspending tatraethyl lead from 100LL fuel. First, the LL means low lead. Second, until somewhat recent years, all gasoline had this additive in it, probably more than the 100LL does. In forty years of working on engines that ran leaded and ran no-lead, I did not see any differences or problems with lead build-up in engines that had oil changes as they should.
Regards Marti

maybefixit · 04-06-2009, 17:24

Hm. I'd recommend doing some searches in the EAA (Experimental Aircraft Association) websites, as they work with classic certified aircraft, restored warbirds, and amateur-built aircraft.

I'm curious about where you found that statement. As a pilot, I'd think the best reason not to use auto oil in a certificated aircraft (commercially built) is that the manufacturer did not allow it, and you'd be risking your license if a crash occurred using non-aviation approved oil (even if it had nothing to do with oil).

Obviously, there are air-cooled cars (VW beetle, Corvair, etc) that use regular auto oil, air cooled engines in the civilian generator, lawn care, and tractor markets, and motorcycles that use automotive (or automotive style) oils just fine. I don't think the key is air versus water cooled, especially when so many V-12 engines in WWII were liquid cooled (P-40 Warhawk, Mustang, P-38 Lightning, ME-109, FW-190, Spitfire). An airplane's power curve is a lot like a generator with a high constant speed, but aircraft must expect wider temperature variations (below freezing at high altitude on a 65 degree airport day).

I doubt that brass corrosivity would be an issue with either oil, as most engines have some brass components in them somewhere. Oil corrosion is a byproduct of water in the oil, from condensation, and the ability of the oil to buffer that acid formation is important (and one thing that I understand aircraft oils are formulated for - since the vehicle often sits several days between flights).

The oil additives are an issue, which is why motorcycles recommend 10w-40 instead of other grades, as that grade usually has the right additives to help the transmission (and why that grade does not carry the 'energy conserving' mark inside its ratings circle. As I understand it, the engine part of the motorcycle system would be fine with anything.

Quoting the Pilot's Operating Handbook for Cessna 172M (1976) they require:
Aviation Grade SAE 10w30 or SAE30 between 0F and 70F, SAE 10w30 or SAE20 below 10F. They also cite MIL-L-22851 except for the first 25 hours when a straight mineral oil of MIL-L-6082 is used.

I'd expect that one key difference in the aviation grade oils is bureaucratic; the aviation grade oil will have better records to prove to the FAA after a crash that the oil from that manufacturing lot was up to snuff. It seems to be a key difference in many other aircraft parts, such as belts and hoses.

Some of the experimental aircraft owners I know use a good synthetic auto oil in their engines, and some use aircraft oil. Many of them are using converted auto engines to fly. I expect the military used a good quality land based oil for the generators, so I wouldn't think you'd cause a problem doing the same.

The 100LL fuel is a low-lead, but that's compared to the over 130 octane that used to be available, which was a higher concentration by far. There is still notable lead in the fuel. As I understood it, the lead tends to foul the spark plugs and can build up on the valves more so than getting into the oil. I mostly got working on cars as lead was being phased out. I know there were a lot of discussions in magazines about changing the valve seats in 60s-70s musclecars during restoration so they could handle unleaded, as the lead helped reduce exhaust valve seat erosion.

There are allowances to let low-horsepower certificated aircraft fly using auto gas (91/93 unleaded) IF there is no ethanol in the fuel,and the right paperwork has been filed. So clearly there are a lot of similarities between the oils and fuels at this point.

I'd say if the PM's for your generator specify an auto grade oil, then run with that, since the designers of the engine knew they'd be using that oil, and it's probably cheaper than buying aircraft oil. I always figure that oil I'm buying today is better than racing oil from 15 years ago, so I don't get too worried about oil quality (other than not buying the cheapest stuff Auto Zone sells - it smells funny).

cranetruck · 04-06-2009, 18:03

Interesting (this is all academic , but interesting in any case). The genset LO calls out OE/HDO (MIL-L-2104), which is different from the OE (MIL-L-45199) specified for the multifuel engine for example.

The quote at the beginning of this thread came from one of the hits while doing a google search for ultralights and the 4A084 engine, which is sometimes used in that application.

"AeroShell Oils and AeroShell W Oil is intended for use in four-stroke cycle aircraft reciprocating piston engines. The term “ashless dispersant” was given to aviation oils to distinguish them from straight mineral aircraft piston engine oils. Because of the negative effect of ash on aircraft engine performance, it is very important that ash-containing oils are NOT used in an aircraft piston engine."

Edit: Added image and quote from AeroShell aviation oil note.