Aviation Engine oil - Anyone know much about it?

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I was at a local oil distributor for work yesterday and they had Shell 15w50 and Phillps 66 XC 20w50 and 25w60. I was talking to the counter guy and said it was about $25-30 per gallon depending on the brand and weight. He stocks it for some of the local people in a flying club. He was talking about how unique the oil formulations are due to having to protect at high altitudes. He said they are all

Does anyone have experience with this oils? How much different are those multigrades than compared to PCMO? What do the additive packages look like? Do they use the same type of base oils? How does the pressure differences at 35,000ft change the oil properties?
 
do NOT use aviation oil on a car. They have very weak additive packs to prevent spark plug fouling. BTW, they don't fly at 35k.
 
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What little I know agrees with what Doog said. The big deal with aviation oils is to prevent combustion chamber and plug fouling. Aviation reciprocating engines have a very short time between planned overhauls, so minimizing wear is secondary to 1) preventing wear well enough to prevent a catastrophic failure, and 2) preventing fouling the plugs leading to an engine failure.

Altitude has little to do with it. Its COLD up there, but the engine is running and the oil kept hot, though during descent the oil can cool down as the engine has little load on it.
 
Originally Posted By: 440Magnum
Altitude has little to do with it. Its COLD up there, but the engine is running and the oil kept hot, though during descent the oil can cool down as the engine has little load on it.


+1 Plus think about the aircraft moving about climbing and diving which is similar to accelerating and engine braking in a car.Oil gets sucked past the rings and has to combust in the engine readily without fouling the spark plug. This happens repeatedly and the oil picks up lot of combustion by products as well. So, these oils get changed often. Anti-wear additives are secondary.
 
Originally Posted By: expat
They seem to be very thick!

Why?


Aid compression. Resist shear. Remember: Compression is power.
 
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Originally Posted By: Doog
do NOT use aviation oil on a car. They have very weak additive packs to prevent spark plug fouling. BTW, they don't fly at 35k.


Good warning, they often have zero anti wear or EP additives, just a little detergent. Aero engines rely on thick oil film to protect rings and bearings because compression lower. Some are straight single grade oils.

New car engines in USA using thin 20 grades that rely on their AW and EP additives for protection much more than oil film thickness. Opposite approach to aviation, because of fuel economy not long term wear factor in extreme operating conditions issues.

Germany full of well educated engineers, so they have changed nearly all the original 0 or 5/30 recommendations at garage chains to 0 or 5/40 car oils, for older engines. New ones still use design spec 0 or 5/30, except hybrids or a few Fords built with higher tension rings (They will wear out faster in severe use) and smoother bearings (They don't retain oil film after shut down so well, so cold start wear increases). Those engine must be run on recommended 20 grade oil when newish, with short OCI to keep additives working, putting an aviation oil in one would kill it real fast.

Note: spark plug fouling was caused by Lead in older types of fuel, now they use low lead 100LL in piston engines. Too much Zinc might be bad, as they run cooler. Certification of aero oils takes into account potential errors at oil producer. Very tough to make error with base stock viscosity and easily detected. Mistakes have been made with additives, so aviation oils are all OK with zero.
 
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Originally Posted By: expat
They seem to be very thick!

Why?


Most aircraft engines run 100 octane low-lead fuel, they crank out high compression, high RPM, burning along at cruising speeds for hours upon hours with only airflow to cool it.

Tends to be a bit of an abusive relationship :p
 
Originally Posted By: RiceCake
Originally Posted By: expat
They seem to be very thick!

Why?


Most aircraft engines run 100 octane low-lead fuel, they crank out high compression, high RPM, burning along at cruising speeds for hours upon hours with only airflow to cool it.

Tends to be a bit of an abusive relationship :p


LOL, quoted for levity
 
Most aircraft piston engines are low compression, less than 9:1 and low max RPM 2700RPM is common. However relatively high load and constant RPM.
The average 4cyl 360 CU in engine is rated to 180hp at max power.

I reckon the oils would be low spec due to the age of the technology and age of the required standards.

Piston engines have large clearances and usually require zinc to stop the cams spalling (common) and corrosion inhibitors as the dont get used regularly.

They run fuels full of additives to prevent detonation in their huge cylinders and extra additives to scavenge the octane boosters. Plug fouling is a huge problem at my company.

The dye in the fuel can also block fuel injection systems.
 
djc,
whereabouts in S.A. are you ?

I used to live within spitting distance of Parafield, and today had a lovely conversation ate a BBQ area with a couple from Adelaide.
 
A while ago, maybe last year, I saw some Aeroshell 15W-50 on CL at an attractive price.
I thought that it might be fun to run this synthetic blend oil in the BMW and then UOA it.
Shell's TDS shows a VI of 160 as well as ultra low SAPS and sulfer.
It also specifically states that this oil is not recommended for use in automotive engines.
Now, this oil is said to be formulated with a non-metalic antiwear package and incorporates a Lycoming anitwear additive.
There are two piston single UOAs of this oil in that forum.
One looks very good while the other looks pretty bad.
Bottom line is that I decided that this oil might be okay for short interval PCMO use or might not, so I passed.
Incidentally, the engines the oils you cite in your original post are used in will see 35,000' only in an altitude record attempt using glider techniques or if shipped as cargo in an airliner.
 
Since the oil I saw was not for airliners, what kind of oil do planes like 737 and A320 engines use?
 
An ester based oil intended for turbine engines.
The oil should never see combustion products or mechanical shear, FWIU.
It need only survive high heat while providing lubication to the engine's shaft bearings.
Aeroshell 15W-50 for piston engines runs a reasonable ~68.00 for a case of twelve quarts.
Aeroshell turbine oil comes in three flavors for different application requirements and ranges from a still reasonable ~$232.00 to ~$270.00 for a case of tweny four quarts.
Mobil Jet Oil runs ~$290.00 to ~$315.00 for a case of twenty four quarts from the same vendor.
 
Originally Posted By: volk06
Since the oil I saw was not for airliners, what kind of oil do planes like 737 and A320 engines use?


This old thread will give you more than you probably want to know about jet engine oils:

Jet Turbine Oils

Tom NJ
 
Originally Posted By: RiceCake
Originally Posted By: expat
They seem to be very thick!

Why?


Most aircraft engines run 100 octane low-lead fuel, they crank out high compression, low RPM, burning along at cruising speeds for hours upon hours with only airflow to cool it.

Tends to be a bit of an abusive relationship :p


There, I fixed it ;-) Aviation engines for the most part turn LOW revs compared to their boat and automotive counter parts. Smaller aviatioin engines found in Cessnas and Pipers are direct drive, and even the huge WWII radials and V12s with reduction gearcases are considered absolutely screaming if they reach 3500 RPM. The low speed / high torque operation really pounds on bearings (which are huge to tolerate it), and rejects a lot of heat through the pistons to the oil. Aviation oils are thick because they get very hot at times, and also for the thick film protection mentioned earlier.

Oh, and that 100LL avgas has more tetraethyl lead than almost any automotive fuel EVER had. Old high-lead avgas must have been practically silver. :p
 
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The concept of this oil interests me suddenly as a new rotary owner recently posted elsewhere of buying an RX-8 from a gentleman who was using aviation oil in the car. For a rotary where oil needs to burn clean might not av oil be a better choice over pcmo? At least on short oci's?

Is there any hard published distinctions between the 2 oil types?i
 
My Cessna Cardinal has a 200HP Lycoming engine. I use 15W-50 in the Florida winters (I do travel North) and Aeroshell 50 in the summer.

I cruise at 2600 RPM, at as much power as I can get the engine to produce at the current altitude. 2700RPM does not improve speed or climb rate at altitude, so I don't operate there.

The heavy viscosity oil is required to provide sufficient protection under high load conditions. Including camshaft and lifter protection. Those who experiment with thin oils in hot conditions, end up with problems.
 
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