Mystery Oil for old & new cars?

March 1, 2008 | By Richard Prince


In the letters section of a previous issue a gentleman stated that he uses outboard oil mixed with his gasoline to keep his rings and valves lubricated. I know that Marvel Mystery Oil used to be sold for this purpose too, but how valid is this practice today?

And I ask this question in reference to old and new cars. My old cars, which still would prefer leaded gas, are one thing, but what about my newer ones like my wife’s BMW and my Ford diesel Excursion? Would this practice harm the fuel injection system? What about my oxygen sensors?


Marvel Mystery Oil will not harm modern electronic fuel injection components or oxygen sensors, and, in fact, is safe to use in your newer cars.

That does not, of course, address the question of whether Marvel Mystery Oil or other similar products are necessary.

My gut feeling tells me that in most instances they are not. I have no doubt that older cars in particular can benefit from the upper end lubrication that Marvel Mystery Oil offers but I think an important variable is how many miles you drive your collectibles.

If you put a thousand or so miles per year on an older vehicle then I don’t think you need to worry about additives to lubricate the upper end.

Conversely, if you’re driving 8000- 10,000 miles per year, and your engine has not been modified with hardened exhaust valve seats, then I’d certainly recommend using an additive to compensate for the absence of lead.

Your new cars were designed to run on today’s fuel so I wouldn’t be particularly worried about top end lubrication.