Spinning Levers, LLC

We change aviation oil because it becomes corrosive.

In our piston aviation engines we don’t change the oil due to oil breaking down and losing it’s ability to lubricate the engines, it’s more because the oil gets contaminated with all kinds of stuff and we need to remove it from our engines.

As you run it, then let it sit for a bit, the contaminates picked up due to combustion will become corrosive. Nothing like a corroded engine.

Byproducts of carbon, oxides of nitrogen, sulfur, raw fuel, and partially burned fuel leak past the piston rings and contaminate the crankcase. The worst of these, and the most corrosive, is dihydrogen monoxide (DHMO). This stuff gets by in relatively large quantities and pretty harmful when it builds up in your oil and comes in contact with parts like camshafts, lifters, crankshafts, and gears.

Then you have to deal with avgas, which has healthy doses of an octane improver called tetraethyl lead (TEL).

How often?

Changing the oil that has these corrosive elements suspended in it is the main reason for the 25 or 50 hour (or 4 months) change intervals.

Your oil has proprietary additive packages mixed in it. Most importantly acid neutralizers. They do in effect, neutralize as much as they can and you have to change your oil to replenish these engine protectors. It’s like your oil can only hold or effect so much stuff and it’s “full” or “used up” I guess you could say!

If you’ve ever seen baking soda neutralize battery acid, that’s a pretty good illustration of how the oil neutralizes the corrosive byproducts of internal combustion that gets past your piston rings.

I’ll take a deeper dive into oils in another article, but know that our low RPM, low operating temperature, wide dimensional clearance engines really have modest lubrication requirements as compared to a higher revving car. Just about any brand of type of aviation oil can satisfy our engine’s requirements.

Want to make it to/past TBO?

Rust is the #1 reason that engines don’t make it to the manufacturer’s recommended TBO. The engine builders themselves recommend that owner-flown aircraft that fly irregularly are at high risk for rust damage and they’re better off using a thick single weight oil (Aeroshell W100 or W100 Plus). It’s also a good idea to add some CamGuard as well for additional protection. Cheap insurance.

DIY?

FAR 43 appendix A lists oil changes under “preventative maintenance” and a pilot who isn’t an A&P or repairman can do it without supervision. Hey it can get messy, so it’s not a bad idea to ask for tips, ideas, or a 2nd set of hands especially if it’s your first time doing it. Save yourself some money, learn a bit about your engine, and know it was done correctly because you saw it! Bit of peace of mind and that’s always nice to have!