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Piston install lube

Engine Building Fundamentals

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Hi,i also read in a number of books that using ATF fluid is good if not the best to lube the cylinders upon assembly,even using it as a cleaner prior to install.Is this true and applied,or is mineral oil a better option?

I've never used ATF and don't really see any reason to change from mineral oil. I've always got a ready supply of clean mineral oil on hand for other aspects of the assembly so it makes sense to just use that.

I and others have always used ATF and never had issues. I learned about ATF 30 years ago as dirt track racers would use the ATF to assist the ring seat process because they used a fine cross hatch on the cylinder walls. The lower RA combined with thicker oils wouldn't allow the rings to seat. (I believe Iron rings was your only choice back then. But I know some local engine builders that have never used anything but ATF and have a great track record.) I put ATF in a squirt bottle, apply to the rings and grooves right before I install the assembly. Before installation of piston assembly I will apply ATF to the cylinder walls.

HINT: ATF works good at keeping flash rust at bay. When I get the block from the machine shop I will clean it and clean the bores and journals until I can wipe with a white paper towel without residue. Then I will apply ATF to the bores and journals, some times the ATF will loosen more particles as ATF has strong detergents as well as anti-rust properties.

You can pour a little ATF in your Dailey Driver about 500 miles before an oil change to keep sludge and coking down. Especially if the vehicle typically makes short commutes that never allows the engine oil to get up to temperature long enough to expel all the moisture. I would not add ATF into a higher mileage engine as it's possible to dislodge chunks of sludge that can clog the oil pick-up. (Castrol Oil was the worst with sludge IMO. Being Toyota promoted Castrol, Toyota engines got a reputation having sludge build up. Honestly I believe it has more to do with operating temperatures and run time at temperature.)

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