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Best additive to get rid of varnish in fuel system

14K views 8 replies 5 participants last post by  expotruck 
#1 ·
I used about 2 gallons of old gas in moment of weakness and now fuel tank and system has a lot of varnish in it. Drained it a few times but too late. Varnish is growing. What is best additive to clean? Even if I boil or change the tank the varnish is still in lines and fuel log. Truck drove okay but tank stunk and problem not getting any better.
 
#3 ·
Varnish forms in fuel systems that have sat with fuel stagnant in them for extended periods. Running a few gallons of bad gas will not likely cause this varnish buildup unless it was allowed to sit stagnant in your truck.

As long as the fuel did not sit in the truck for long, a fresh tank of fuel and any decent additive should have it back to normal in a tank or two. Varnish will not grow or plug up fuel lines, it will gum up small pasages like injectors or carburetors. Avoid additives with alchohol as they attract moisture.

Although ATF has detergent properties, it is not advisible on any modern engine. The ATF oil may clean the fuel system (it will do just the opposite if left in the fuel for long) but also plug up the catalytic converter.
 
#4 ·
Thanks for replies. Vehicle not licensed so dont go through a lot of gas, but ran at least every few days. Tried stabil but seems to have no effect, maybe even worse. Changed tanks now but varnish still in lines etc. Saw on diesel site someone did gas chromatography on seafoam and it was almost 100% kerosene. Was looking for some sort of varnish dissolver. Industrial strength gumout or similar.
 
#8 ·
I changed tank, changing injectors now, will do filter before I run it. There is a varnish buildup on inside of lines and fuel rail. How do you clean those?
 
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