Gear Box Question

I'm about to do my first oil change and wondered if I need to change the gear box oil on the same schedule. From what I'm seeing it appears the gear box shares the engine oil and when the engine oil is changed ergo the gear box oil gets changed. Is this accurate?

No, Amadeus, the gearbox does not retain that much oil and after shut down, most drains out. I took the attached photo of my gearbox housing when I removed mine. Very little oil leaked out when I removed the gearbox. When you remove the magnetic plug, you’ll find no oil leaks out there either.

So when I change the oil I will be actually changing the oil in the gear box, as well?

Let’s answer it in a different way… the oil you remove from the oil tank circulated through both the crankcase and the gearbox.

I don't know why you got such a roundabout reply, Amadeus. The answer to your queestion is simply YES. You do change the gearbox oil when you change the engine oil.

To further clarify, it is not a separate operation. Change the engine oil, and you have simultaneously changed the gearbox oil.

Thanks!

My hangar mate has a Zenith 750 Cruzer with a Viking (Honda Fit, originally) engine that has a completely separate gear box and he posed the question of the maintenance schedule for the gear box and if it gets changed each time the engine oil is changed. After hours of scouring through everything I could find about the gear box I never came across a maintenance schedule for it specifically.

There are RV-12 owners, including one flight school that I am aware of, that run Mobil 1 4T RACING Motorcycle 10w-40 full synthetic motor oil, due to it's gearbox additive, which suits the purpose of a motorcycle motor oil that shares engine and gearbox duties.

If you do decide to run this full synthetic motor oil, understand that you can run very little 100LL in the engine while on this motor oil. It requires almost exclusively Premium UNLEADED Mogas. Full synthetic motor oil does not suspend lead well in the motor oil.

A Rotax 912 and a Honda car engine are two different critters. See if someone else at your airport also owns something Rotax 912 powered plane for a better powerplant experience. Or ask here, there's hundreds of years of Rotax experience combined, here on VAF.

NinerBikes said:

There are RV-12 owners, including one flight school that I am aware of, that run Mobil 1 4T RACING Motorcycle 10w-40 full synthetic motor oil, due to it's gearbox additive, which suits the purpose of a motorcycle motor oil that shares engine and gearbox duties.

If you do decide to run this full synthetic motor oil, understand that you can run very little 100LL in the engine while on this motor oil. It requires almost exclusively Premium UNLEADED Mogas. Full synthetic motor oil does not suspend lead well in the motor oil.

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Is the Mobil 1 4T Racing oil approved by Rotax? I never use 100LL and instead use a 50/50 mixture of 93 Octane Premium Unleaded and 90 Octane Ethanol Free Unleaded.

Amadeus said:

Is the Mobil 1 4T Racing oil approved by Rotax? I never use 100LL and instead use a 50/50 mixture of 93 Octane Premium Unleaded and 90 Octane Ethanol Free Unleaded.

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You'll have to do your own research on that. I know it was approved by Rotax at one point in time. Talk to Glass Cockpit Aviation in Boise ID, they run it in their RV-12's in their flight school, owner is an AP and is Rotax Heavy certified.

Rotax Service Instruction SI912-016R13 shows only AeroShell Sport Plus as being approved. Older revisions of this SI allowed other oils like Mobil 1.

I recall the reason is that Shell agreed not to change the formulation without Rotax approval.

Jim Butcher