Found this an interesting thread on www.bobistheoilguy.com

Urban myths:
-you can't switch to synthetic from dino in an older engine
-using trans fluid to clean an engine

Both are old wives tales,


Don't have any links, but let me try to help in simple terms.

ATF is somewhere in the same viscosity as a 5W-20 motor oil. ATF does not have near the detergents in it that a well formulated engine oil has. So, ATF has no more cleaning power (actually less) that a good 5W-20 oil.

Here is where the old tale of cleaning came from. Most of it started back in the 50's when everyone was using low grade single weight oils. The cleaning effect has more to do with viscosity than anything else. Example: Put a big wad of grease in your hand and rub you hands together. Now, pour some 30 weight oil on your hand and rub them together. You will see the oil try to clean the grease. Now, pour some ATF in your hand and you will see a little more cleaning. Now pour some liquid hand cleaner/soap in you had and the cleaning will continue. Now, pour some kind of solvent on you hand, i.e., gasoline, kerosene, etc., and the rest of the grease will come off. The lighter the viscosity of the fluid the better it breaks up the grease. Now granted the liquid soap and solvent have oil/grease cutting agents in them, but the ATF does not.

All ATF is, is a light weight oil with additives in it to make an automatic transmission work. Called Friction modifiers. There is NO intentional cleaning effects with ATF. Actually the right way to clean an engine is to use auto-rx and do it right and do it slowly.
Using Seafoam is just too agressive as well.
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I don't agree with you on this one Fred. I would never use Seafoam or Auto-Rx to clean a sludged up engine. Just run synthetic in it for 500-1000 miles, change the oil, and change it again in another 1500 miles. This will do a good job of de-sludging the engine without using questionable engine 'cleaners'...

 

You are entitled to disagree on the usage of Auto RX and Seafoam to clean an engine.

My point in this thread was just to give some insight into an old wives tale regarding using ATF to clean an engine. It doesn't.

My second point was to say if your intention is to clean up an engine suspected of sludge, there is a very widely accepted method of doing so. And that is using Auto-Rx. If you want to know where I get my info from go to www.bobistheoilguy.com and read the section devoted soley to this method. It is universally accepted as a great, and safe cleaner. Certainly not questionable.

I would NEVER use seafoam in my engine oil, ever. That could even damage seals long term. It's way too agressive.

Using synthetic oil for the purpose of cleaning an engine (if you use the right one like Redline or PP) can't be argued. From what I read it will clean out some things, but auto rx will do the entire job for the same pricing.

Maybe I am biased since it's (ARX), in the Power steering and engine sump of my S70 T5 right now. Actually it already is out of the PS, from yesterday and had to flush it out twice since the fluid was so dark. Took almost two quarts but is back to Red color. Steering is noticeably quieter and smoother. It won't come out of the oil sump for another 1000 miles. Luckily I have no leaks on the engine right now, but I want to keep it that way. I have replaced a half dozen hoses from the oil cooler to the turbo, but that's not the cars fault. Thats just old age of the prior hoses.