Fuel system cleaner - will it clean lifters?

[Dr. T]

Will a fuel system cleaner clean out stuck or dirty hydraulic lifters? If not, what will? Oil addatives? Which one(s)? What about cleaaning valve seals and stems?

 

[MolaKule]

If you take the dirty hydraulic lifters out of the engine and soak them, sure. I would not recommend putting this stuff in a motor oil.

Neutra, LC, or AUTO-RX in the motor oil should clean the lifters over time. Worn valve stem seals need replacement if engine is smoking on deceleration and startup.

Here, Neutra, LC, or AUTO-RX might clean up seals and remove the sludge so they are more flexible.

 

[Dr. T]

What about OTC products like MMO or Gunk ValveMedic? Are they safe to add to oil for this purpose?

 

[TC]

As always, MolaKule has some great advice. If you simply want to take care of a sticking lifter, a cheap option might be to use a "rude and crude" over-the-counter product like MMO, Rislone, or Gunk, as you mentioned. See below for the formulation of these products, which is often some mixture of kerosene, mineral spirits (paint thinner), naphtha, mineral oil, etc. I know from experience that MMO will often clear up noisy lifters. Should you use any of these solvent cleaners, I'd suggest carefully following the label (more is not always better), use them only as long as needed (not a routine addition to your oil), and avoid using them if your engine is truly dirty (you see substantial grit, varnish or sludge through the oil filler cap) since such products can dislodge enough "gunk" to potentially clog oil passages. Should you have such an engine, then the better "go slow" products recommended by MolaKule are pretty much a MUST.
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