Does MMO actually help aircraft engines, whether added to the oil or the fuel?
The infamous MMO debate continues. Given there are thousands of other opinions on the topic, just take my opinion for what it’s worth -- 2 cents. But first to put it in context.
Decades ago, when MMO, Seafoam, and other similar additives were first developed, petroleum lubricating oil technology was in its initial stages. So most lube oils were raw and nothing like the high-tech oils we have today. This is the reason MMO and the others were definitely “needed” way back then and especially in radial engines. This is also why any round-engine mechanic worth his weight is a diehard MMO user.
However, since the mid-50s, petroleum then synthetic oils have become a mixture of various chemicals that for the most part provide the same results as MMO just through other means. So in most cases today adding MMO does not give much benefit as the oil already has similar additives added to it.
That said, MMO still has a place but more as solution to a specific problem than as an overall preventative measure. Personally, I only use MMO in radial engines that do not fly on a regular basis and in all non-Honda 4-cycle small engines like lawn mowers, etc. However, I only use it in the oil and not the fuel. For small engine fuel I use Seafoam.
Is there any actual data supporting their claims for engine improvement?
I’m sure if you dig deep enough you’ll find some report that states MMO does improve something, somewhat. However I don't recall MIT or Cal-Poly ever releasing any report on MMO. Outside of radials running straight conventional oil, I've personally only seen MMO actually provide a permanent marked improvement in a small group of aircraft. But these aircraft also had existing issues as well. So to say it’s the proverbial mechanic-in-a-can, I tend to believe its glory days were 70 years ago vs today. But what do I know… MMO just came out with a synthetic version. As the rotor turns we say on my side the fence.
And as a side FYI: we can thank the railroad industry for the improvements to lubricating oil technologies to include the use of oil analysis in monitoring engines for potential failures.
