I read over this Liquid Moly forum and now I want to use Liquid Moly, even though my current highest mileage vehicle has 32k on it.
When I first started driving the oil change interval was 3000 miles. I would swear it ran better after an oil change. In my view, with today's engines and advanced synthetic oils, when we use additives and change out parts prematurely, we are making ourselves feel good. And nothing more. Meanwhile, I see no reason to use an oil additive on a vehicle that has been properly maintained and the valve train looks clean through the oil fill hole.
Manufacturers (almost?) universally say not to use oil additives. There has to be a reason for this.
I never did use oil additives like STP or Lucas, or varnish removers, with one exception. I had a used and abused old Chevy truck from the 70's that was too tight to crank easily when hot, and I think I used Rislone engine cleaner to free it up, and that additive worked. I never used oil additives again. I do occasionally use Chevron with Techron fuel additive, and I can hear a slight difference at the exhaust pipe - it noticeably smooths out the exhaust note after several years without it.
I had a new 2000 Honda Odyssey that went 248k in 15 years. It ran fine and didn't burn oil. A cow ran into it, then it went to the boneyard. I changed oil annually or sooner, used Mobil 1 Extended Life for most of its life, and ran it up to 14k on extended trips, which is what I used it for. I used Mobil 1 filters, often with every other oil change, because a clean engine won't particularly plug filters. The engine issues were the EGR valve, the Idle Air Control valve, belts, and a gasket or two. Everything else was normal maintenance, like timing belts, plugs, belts, etc, at normal recommended intervals. I never saw varnish on the engine internals when I did a valve adjustment at about 180k.
I have better uses for my money than oil additives.
