Toyota Truck Tips: Can ATF Make Your Engine Last Longer?

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Toyota Truck

Many claim that adding a quart of ATF in with your oil can extend engine life. But is it just an urban legend?

There are so many urban legends and unfounded tips in the automotive world it can be hard to separate fact from fiction. But that’s why we seek out real world advice. In real world places, with real world people. You know, like the Yota Tech forums. It’s here that you’ll find countless experts who’ve racked up countless miles on their priceless Toyota trucks. And the latest tip we came across there is well worth vetting.

It all started with Bill Edgar and his attempt to keep his Toyota truck running just long enough to get a new engine. That’s when notable Toyota experts 22RE Performance suggested something most of us might find a little usual.

“So I talked to a guy at 22RE Performance the other day about a new engine. I told him that mine was running rough and consuming a lot of oil. I was afraid my motor wouldn’t last the 24 to 30 week wait time for one of his engines. He told me to replace a quart of oil for a quart of ATF on my next oil change.

While I was at Autozone picking up ATF, I told them what he said. They said that’s crazy, but hey, they are Autozoners. So I bought the ATF and thought I would follow up on that advice online. I have seen a lot of mixed reviews. What do you guys think? Should I pour a quart of ATF in a motor that has 305,000 miles on it to help it last another 6 to 8 months? The guys at 22RE Performance seem to know their stuff!”

Toyota Truck

You can’t blame folks, including scope103, for being a little skeptical about this unusual advice.

“Googling the concept, I came up with a number of web forums (like this one) where folks were asking about whether adding a quart of ATF RIGHT BEFORE AN OIL CHANGE would help clean out the “gunk.” The general consensus was that this was just an old shadetree mechanic stunt. Supposedly, back in the ’40s and ’50s, ATF had better detergent than motor oil, and so it “worked.” Sorta. Back then. Today, we have much better motor oil, so the general opinion went, and using ATF did nothing but thin out the oil.

Even with Google, I didn’t find anyone talking about LEAVING the quart of ATF in the engine for the multiple month term. Given that ATF is lower-viscosity (I’ve heard it’s about SAE 10) than the oil you should be using, I can’t imagine anything good coming from that.”

On the other hand, many believe that there is some logic behind the idea of running ATF in a high mileage vehicle like the OP’s Toyota truck.

“The guy at 22RE is attempting to slow oil consumption by running some ATF for a while,” says 89fourrunner.“It seems backwards, but it is essentially what Marvel Mystery Oil does. LUCAS on the other hand….how many ways can one company sell gear oil? Ask Lucas. That is all they sell you in practically every product. On top of that, their gear oil is some of the worst on the market! BITOG is pretty reputable and good things have been said about this means of cleaning an engine.”

Toyota Truck

Most prefer to run thicker oil on older, leaky engines for that very reason. It’s a subject that Kolton5543 dives into a little deeper.

“You can do it, but it likely won’t help much but certainly won’t hurt it. ATF is in fact very high in detergents. It has to be because auto transmissions have a huge number of fluid passages and ports that are all very small. If any of them get even a little clogged the transmission won’t work very well. If you ever disassemble a high mileage engine and transmission you immediately notice the trans to be spotless from debris stained into the components while the engine will likely be a bit messy. 

I say it likely won’t help much because ATF is good at cleaning, not restoring. If your engine is dirty and it leaks it’ll likely leak a bit more afterwards. If you’re burning oil, then your engine is just worn out and only thicker oil would help slow it down. ATF does thin the oil, but not significantly. I’d recommend only a half a quart and just leave it there. I’ve used as much as a quart before for a couple hundred miles to clean badly sludged engines and help with noisy dry starts. Sometimes I’ll just add a little at an oil change just to keep things clean. The moral of the story is give it a shot if you want, but it won’t help the life of your worn motor.”

So perhaps the ATF trick isn’t exactly the miracle cure that some make it out to be. But we want to know what your thoughts are on the matter. Have you had any luck with adding a little ATF to your oil? Or, on the other hand, have you had a bad experience after doing so? Head over here and chime in with your thoughts!



Brett Foote has been covering the automotive industry for over five years and is a longtime contributor to Internet Brands’ Auto Group sites, including Chevrolet Forum, Rennlist, and Ford Truck Enthusiasts, among other popular sites.

He has been an automotive enthusiast since the day he came into this world and rode home from the hospital in a first-gen Mustang, and he's been wrenching on them nearly as long.

In addition to his expertise writing about cars, trucks, motorcycles, and every other type of automobile, Brett had spent several years running parts for local auto dealerships.

You can follow along with his builds and various automotive shenanigans on Instagram: @bfoote.

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