Run transmission fluid in place of engine oil?

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Yeah, I'd cringe reading that title as well. Still. A quick question for the maintenance and service/repair community. One of the things I read time and again on the Internet is those that say that, to clean an engine to a spectacular state of cleanliness and de-sludge, is to drain out all the old oil, refill entirely (and this is a part of my question) with ATF, and let it run at an idle until it fully warms up for 15 minutes, or 30, or an hour, no load (again, that a part of my question..) And that the ATF then comes out looking jet black and not the cherry red it did going in, and that the engine then runs phenomenally. My question to you all is simply if this is a real thing, if it is bunk, and if anyone has ever tried, or can verify or de-bunk. Thanks.
 
Bovine Scatology--ATF has no detergents so how will it clean anything? Interesting how these wive's tales carry on through the years.
 
Originally Posted By: 2015_PSD
Bovine Scatology--ATF has no detergents so how will it clean anything? Interesting how these wive's tales carry on through the years.


That is a very good point, however, one of the things I hear repeated frequently is that "ATF is a cleaner" put in quotes because I hear this often.

Some say to put half a quart in a gas tank for cleaning as well.

Also. Wouldnt the engine be horribly harmed by running ATF and not motor oil? How would it even stay running for an hour?
 
Originally Posted By: Turbo_Lemming
That is a very good point, however, one of the things I hear repeated frequently is that "ATF is a cleaner" put in quotes because I hear this often.

Some say to put half a quart in a gas tank for cleaning as well.

Also. Wouldnt the engine be horribly harmed by running ATF and not motor oil? How would it even stay running for an hour?


1. A lot of things are repeated often yet are not true.
2. See #1 above.
3. No. Think motor oil without additives. One hour isn't going to cause harm.
 
Originally Posted By: Turbo_Lemming
Originally Posted By: 2015_PSD
Bovine Scatology--ATF has no detergents so how will it clean anything? Interesting how these wive's tales carry on through the years.
That is a very good point, however, one of the things I hear repeated frequently is that "ATF is a cleaner" put in quotes because I hear this often. Some say to put half a quart in a gas tank for cleaning as well. Also. Wouldnt the engine be horribly harmed by running ATF and not motor oil? How would it even stay running for an hour?
I have seen this posted/discussed through the years as well, but I have never seen results--only talk and again, with zero detergents how will it clean? I suppose an engine **might** idle for an hour on ATF (very dependent on the engine), but I would not want to try it, it would be a pretty thin PCMO.
 
Originally Posted By: kschachn
Originally Posted By: Turbo_Lemming
That is a very good point, however, one of the things I hear repeated frequently is that "ATF is a cleaner" put in quotes because I hear this often.

Some say to put half a quart in a gas tank for cleaning as well.

Also. Wouldnt the engine be horribly harmed by running ATF and not motor oil? How would it even stay running for an hour?


1. A lot of things are repeated often yet are not true.
2. See #1 above.
3. No. Think motor oil without additives. One hour isn't going to cause harm.


Must counter #3 that those that say using ATF in a pinch in an engine if motor oil is not available then are correct..
 
This is a valid technique. ATF is an excellent penetrant and cleans much better than oil.

This works, but I've NEVER seen someone say fill it full of ATF as a routine maintenance step. 1/4 of the sump is a good amount and idle it for 15 minutes before draining. It works well. I have used it as a flush many times, and also Kerosene as a fraction of the oil. This used to be a factory MB method - it's definitely not "bunk" and anyone who says so is asserting that out of ignorance and not knowledge or experience.

I have read heresay of people with engines they knew were trashed and sludged made a last-gaps try. They say they filled it full and ran it a longer period. Different animal.
 
Originally Posted By: Turbo_Lemming
Must counter #3 that those that say using ATF in a pinch in an engine if motor oil is not available then are correct..


Sure why not? Oil is better than no oil. But where have you ever been that has transmission fluid but no oil? Those types of "OMG it's 3AM and I'm here at this wayfar gas station and there's no oil for sale but there's transmission fluid and I'm 40 quarts low should I drive with it 40 quarts low or should I buy some ATF?" scenarios are pretty far-feteched.
 
OP asked, "... and if anyone has ever tried,..."

My friend bought a ticky 2001 Subaru Forester. He did the ATF (Dex/Merc) 20 minute idle and it had no effect.
 
Originally Posted By: Oro_O
This is a valid technique. ATF is an excellent penetrant and cleans much better than oil.
How does it clean?
 
Originally Posted By: Oro_O
This is a valid technique. ATF is an excellent penetrant and cleans much better than oil.

I'd be interested in seeing some actual evidence of such cleaning.
 
Originally Posted By: Quattro Pete
Originally Posted By: Oro_O
This is a valid technique. ATF is an excellent penetrant and cleans much better than oil.

I'd be interested in seeing some actual evidence of such cleaning.



Yes, any SAE tests about this?
 
Originally Posted By: kschachn
Those types of "OMG it's 3AM and I'm here at this wayfar gas station and there's no oil for sale but there's transmission fluid and I'm 40 quarts low should I drive with it 40 quarts low or should I buy some ATF?" scenarios are pretty far-feteched.
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Originally Posted By: Oro_O
This is a valid technique. ATF is an excellent penetrant and cleans much better than oil.

This works, but I've NEVER seen someone say fill it full of ATF as a routine maintenance step. 1/4 of the sump is a good amount and idle it for 15 minutes before draining. It works well. I have used it as a flush many times, and also Kerosene as a fraction of the oil. This used to be a factory MB method - it's definitely not "bunk" and anyone who says so is asserting that out of ignorance and not knowledge or experience.

I have read heresay of people with engines they knew were trashed and sludged made a last-gaps try. They say they filled it full and ran it a longer period. Different animal.


I've done that with using a quart maximum in the crankcase with the rest being oil
Never had a problem with the engine. Did this on a 97 civic and 98 Sienna. Not sure if the ATF made it more cleaner.

I'll never do it again.
 
I've run ATF in my engine oil, but the intended purpose was never cleaning.

When I used to have my 2003 Mercury Sable with the 3.0 liter Duratec V6, I started seeing oil leaks somewhere around 125,000 miles. Simply switching to a HM engine oil didn't seem to result in any reduction in leaks.

I don't remember where I saw it, but I saw somewhere that ATF was rich with seal conditioners, so I figured I'd add some ATF to my engine oil and run it for a while. An OCI consisted of 5.5 quarts of oil, and so I decided to replace about a quart of oil with ATF.

I ran the engine this way for a 3k OCI, and about half-way through, the oil leaks stopped completely. Was it the ATF? I can't say for certain, but if it was, it was certainly quite the coincidence.

... as a side, when I did change the oil at 3k miles, it came out PITCH BLACK - much darker than I was used to. Just an observation.
 
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