Reader Question: Marvel Mystery Oil?

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Here’s the latest reader question, along with my reply!

Paul asks:Thank you for both the sanity check and things mechanical.  What are your thoughts on Marvel Mystery Oil?

My reply: With disparaging Marvel or other additives, such as Seafoam, Lucas, the need for them is probably much less today than it was back in the daguerreotype ’80s, say – when off-the-shelf oil was practically unrefined compared with today’s synthetic/blends and the additive packages they contain. Engines are also more refined; some are very finicky about what they’re fed – so be careful about adding additives to them unless it’s a what-the-hell situation and it can’t make the problem worse.

I have heard that Marvel and some of the others are useful as solvents to safely de-crud an engine that wasn’t maintained well, etc.

There is one aspect of this I’ll change my mind on, though – and that is with regard to fuel stabilizers/ethanol countermeasures. Today’s fuel – most of it – has 10 percent ethyl alcohol in it and – especially in older cars and cars not driven much and in power equipment such as lawn mowers and chain saws, etc. – using additives to prevent the ethanol from drawing in excess moisture and separating out, gunking up the fuel system, etc. is very sound policy.

. . .

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  1. Marvel is great for cleaning parts as well. Spray a bit on and use a brass bristle brush, rinse with Simple Green concentrate undiluted. Good as new.

  2. Marvel mystery oil is great stuff. not only does it do miracles on desludging a badly neglected engine, I ran it in my Cessna 172 as just a bit keeps the valves from sticking. The old Continental was designed for fairly low octane leaded gas, the modern 100LL runs too cool and valves will end up sticking/hanging up- a true annoyance when flying in the middle of nowhere.

  3. Best thing about Seafoam, esp. is to use it to degunk your intake system. But do it by having a vacuum line (post throttle plate ideally) suck the solvent directly from the bottle with the engine running. By the time you put it in your gas tank, it becomes too diluted.