Just for S&G I put a gallon of Marvel Mystery Oil in my ~30 gallon gas tank of 1995 Chevy Tahoe before fill up.
It was going great and smooth, until 40 miles into the gas tank... The misfires started... Multiple misfires, and OBD1 only gave code 32 (EGR code). Over the last couple tanks misfires kept getting worse, even the slightest incline caused a couple downshifts to help the ol´ 5.7L pull the heavy Tahoe.
Today took out the OEM AC Delco plugs that I installed about 10k miles ago and found them to be very wet, most likely with MMO, as it is an oil and doesn't burn off as fast as gas. Replaced the copper AC Delco plugs with NGK Platinums... All I can say is I should've got these plugs to begin with, because the engine is MUCH smoother now. Misfires obviously gone. Engine is smoother than it was before the misfires, and smoother than it was with brand new AC Delco copper plugs.
Moral of the story? Don't put a gallon of MMO in your gas tank, unless it is a 100 gallon fuel tank. 1qt is plenty for preventative maintenance. I just wanted to see what severe overdose will do and it did exactly what I expected it to do.
It was going great and smooth, until 40 miles into the gas tank... The misfires started... Multiple misfires, and OBD1 only gave code 32 (EGR code). Over the last couple tanks misfires kept getting worse, even the slightest incline caused a couple downshifts to help the ol´ 5.7L pull the heavy Tahoe.
Today took out the OEM AC Delco plugs that I installed about 10k miles ago and found them to be very wet, most likely with MMO, as it is an oil and doesn't burn off as fast as gas. Replaced the copper AC Delco plugs with NGK Platinums... All I can say is I should've got these plugs to begin with, because the engine is MUCH smoother now. Misfires obviously gone. Engine is smoother than it was before the misfires, and smoother than it was with brand new AC Delco copper plugs.
Moral of the story? Don't put a gallon of MMO in your gas tank, unless it is a 100 gallon fuel tank. 1qt is plenty for preventative maintenance. I just wanted to see what severe overdose will do and it did exactly what I expected it to do.