Marvel mystery Oil is primarily Naptha with some additives, It has been around longtime, I remember my grandfather using it crank case , motor oil back then was not multi weight and would often cause hydraulic lifters stick . Naptha has some serious detergent qualities so this will clean injectors as well

Lucas is a refined petroleum product like Marvel more similar to 2 stroke fuel additives. You will notice some viscosity when pouring into fuel tank. I like Lucas Products; but since NASCAR affiliation the stuff got kind of expensive. Here in MD like $34 per gallon at Walmart.

So I find MMO to due a great job at a better price. Longtimeengr