Question: My next-door neighbor tells me I should add a quart of automatic transmission fluid to my 2002 Corvette’s gas tank before I put it away for the winter. He says this will keep the gas from gelling and preventing the possible need for a replacement engine. Is this another old wives’ tale?

Answer: I think he’s confusing a couple of good ideas from older times. It used to be common to add a small amount of oil, often marketed as “top oil,”(Marvel Mystery Oil) to fuel tanks to provide extra lubrication for the valves and guides. But this became less and less necessary starting as long ago as the ’60s, back when valve guides were simple holes drilled into an iron cylinder head. Lately, the guides—bronze sleeves pressed into the head casting—are more wear-resistant, because bronze is self lubricating. When we transitioned to unleaded fuel, there were major concerns with valve-seat recession caused by the lack of lubricating lead compounds in the fuel.

Additives to fix this problem are still on the shelves. (See the letter below.) And it’s a common practice to add antigelling additives to diesel engines to keep the fuel from turning into big, waxy flakes in the tank in cold weather. None of this stuff applies to your relatively new Corvette. Moreover, adding ATF to your tank is likely to contaminate the oxygen sensors with zinc or phosphorus compounds. These are extreme-pressure additives, necessary because the transmission has plenty of steel gear teeth sliding over one another—not really a concern in the engine. So save the ATF for the transmission.

Additives to fix this problem are still on the shelves. And it’s a common practice to add antigelling additives to diesel engines to keep the fuel from turning into big, waxy flakes in the tank in cold weather. BTW, diesel fuel can grow algae if it site to long, making certain additives mandatory in low useage diesel engines.

None of this stuff applies to your relatively new Corvette. Moreover, adding ATF to your tank is likely to contaminate the oxygen sensors with zinc or phosphorus compounds. These are extreme-pressure additives, necessary because the transmission has plenty of steel gear teeth sliding over one another—not really a concern in the engine. So save the ATF for the transmission.

With that being said, most gasoline companies put the proper additive in the mixture for all engines, although I think a bit of Marvel Mystery oil in a ’60s or earlier car can’t hurt. If for some reason you end up needing a rebuilt engine, it was not because the fuel needed additives. With the advent of bronze valve guides, as mentioned above, lead additives (lead is a lubricant for the steel valves and steel guides in old engines) and oil based additives are not relevant anymore.

Regardless of your engine needs, whether it is for a rebuilt engine, or for some good engine information tips, check out our GotEngines.com Blog for real world info in terms you understand.