Seafoam OR Marvel Mystery oil?

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RichLo

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I use them for long term fuel storage to keep the non-ethanol gas good for longer periods of time.

I have a 300-gallon gasoline tank that I still need to fill before winter sets in but I'll put a gallon of each MMO and seafoam in it after they fill it.
 

Erik the Awful

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I use MMO as engine assembly lube. That's it. I haven't used seafoam, but if I bought a vehicle and it was carboned up, I'd probably give it a shot.

Back in my rotary engine days, seafoam was a big no-no. Instead we'd shoot a tablespoon of ATF into the leading spark plug holes, spin the motor over a few times, and let it sit a day to free up the apex seals when they were carboned up. Put some new plugs in it and smoke out all the 'skeeters.
 

Schurkey

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If you are going to go to this extreme GM top engine cleaner works ALOT better than either one of those products.
...but you can not put it in the gas tank. Destroys fuel pumps and rubber hose. Rubber diaphragm on the fuel pressure regulator. Rubber O-rings on the injectors.

Sprayed into the throttle body, it could clean the intake and combustion chambers.

I squirt it into the cylinders by removing the spark plugs on a warm engine. Turn the engine over a few times, let it soak overnight. Cleans sticky rings.

Any of this will create so much smoke when the engine runs that the neighbors will call the fire department on you. CARBON in the combustion chamber is readily removed with plain ol' WATER drizzled into the throttle body. Effective, no smoke, dirt cheap.

GM used to (maybe still does) use Top Engine Cleaner as fuel-injector cleaner. Mixed with gasoline in a pressurized container, then connected to the Schrader valve on the fuel rail. Disable fuel pump. Run engine at fast-idle until the little pressurized tank goes dry. They actually had to issue a service bulletin on the pressurized tank--the Top Engine Cleaner was eroding the copper tube inside the tank. This was about a thousand years ago--1985-ish.

I buy a 20-oz bottle of Techron, and dump it in the gas tank at each oil-change time. Cleans the in-tank gas gauge sending unit, cleans the tank, cleans the injectors--doesn't screw-up anything else.

Those of you dumping MMO or Seafoam in the gas tank at each, or every-other fill-up, better start considering what the octane rating of that crap is.

MOSTLY, stop buying ****** gasoline. Whenever I can, I buy gasoline from a station that advertises "Top Tier" fuel, which has ADDITIONAL detergent in it to keep the fuel system happy. Note that "Top Tier" has NOTHING to do with octane ratings--you can buy low-octane Top Tier gasoline, or "Premium" "Top Tier" gasoline, with or without Ethanol. "Top Tier" signifies ONLY the added detergent.

https://en.wikipedia.org/wiki/Top_Tier_Detergent_Gasoline
 
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454cid

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The GM Top End cleaner has been reformulated a couple of times, now. I've got an unopened can of one of the older versions.
 

Deancr11

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Been using MMO about 40 years now I guess I'll stick with it. Hell have seen it do some amazing things. Then again I'm not real big on change
 

Erik the Awful

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When I was a tech we used BG engine cleaner. We'd get an A/C can tap and plumb it into the air filter snorkel so that it cleaned everything from the throttle blades to the pistons. Stick a zip-tie in the throttle so it stays at 2000 rpm. Open the valve on the can tap until the engine drops a couple hundred rpm, and let it sit until the can is dry. It worked great, but I think we charged about $150 for the job, which was outrageous for the work involved.
 
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