1993 international 4900 w/flatbed

Not to get off topic, but ive got a question about this marvel mystery oil. Ive heard about it before, and have seen it on the shelf at the auto parts store, but what is the benefit of running it through the fuel system? Is it a cleaner and you only use it once in a while? Or is it a lubricant additive that should be run on every tank? I also have an old mechanical, b model cat, so is this a mechanical thing or electronic motors too?


about timing: unless you have a timing meter you really cant time it yourself. Have a shop do it, itll be costly(250-350) but it will really help throttle response, fuel economy, and like the others have said your egt. If its running good now you prolly dont need to get it retimed, but if cold start smoke lingers too long(more than 2 minutes at 45-50 deg f) or you can audibly hear a miss them i would def recommend it. Some engines(such as my b model) run better when set to non stock timing specs, if youre gonna get it meter timed and spend the money you may as well get it timed to the specs other guys have the best luck with.

 

Marvel Mystery oil is a lubricant with scents, and various "unknown" ingredients added.

In Alaska, especially inland or north slope, the extreme winter cold requires arctic diesel, which is as close to stoddard solvent as you're going to find. No lubricity whatsoever, and it feels and smells a lot like paint thinner.

Fuel system mechanical parts typically have an extremely short life - generally about 1/5-1/10 of normal when running on it. The inclusion of 2% Marvel Mystery Oil in arctic fuel reduced wear in the fuel system parts to about "normal". ( My own experience, being the technicial who actually rebuilt the fuel system itself - injection pumps and injectors )

I have also seen 150K mile NA 6.9, 7.3 and 6.2 and 6.5's running normal fuel, that would, by then, have been barely moving because of wear in the pump and again, with the addition of 2-4% marvel mystery oil in the fuel, show negligible wear, and the injectors would appear barely used, instead of being carboned up, galled, and having heavy wear.

I have put it in motors that had loud valvetrains and severely smoking, and seen them go quiet and stop smoking entirely in 15 minutes, in a concentration of 15% MMO.

It is a lubricant and a cleaner.

Not really a marvel, but it is quite effective at a number of things.