They are both safe to use in your crank case
I use marvel because it has been around soooo long and these old dudes that I work with swear by it,
Talking about how in wwii marvel was mandatory military issue because it was so good at keeping things clean and running
Sea foam is similar
Atf can do the same thing so can diesel oil. So pick your poison.
What you are after here is a concentrated dose like a full quart of marvel for the next one or two oil changes
Valvoline is fantastic
Mobil ones is fantastic
I have proven to myself that Mobil one breaks up sludge and will bust up carbon over time, and will restore oil pressure in engines effected by
Sludge
so Mobil is what we run in engines that need it. I switch back and forth between Mobil and valvoline in my rigs based on cost and availability
Here’s some reading about mmo
Is it snake oil? I don’t think so
Because we have actually seen it work. Engine has 0 oil pressure at warm idle
Several heavy treatments later oil pressure completely resorted, seen it with my own eyes more then once
This may sound like an odd question.. does anyone actually use this in their aircraft? I was talking with an owner of a '74 Beech C23 (180hp Lycoming) in Texas.. says he adds it to his fuel regularly and to oil at oil change every 50hrs. I'm very hesitant if not skeptical.. Any thoughts on this?
www.pilotsofamerica.com
The best oil is
Clean oil
These days you can hardly even buy conventional oil anymore, all of our modern oils are very good