Mix auto transmission fluid in diesel fuel?

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Porchhound

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Joined
Jan 6, 2022
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1981 CHB 34

When I purchased my Chevy 2500 (used) my mechanic advised putting a cheap quart of transmission fluid with every 20gal of fuel during fill-up. Since then I've put 120K miles on the truck with no injector issues. Does this process make sense in a marinized diesel environment?
 
Question is would you have got 120K miles without doing this?

L
 
If you get 500,000 miles....that may say something....Plenty of light truck diesels getting 300,000 to 400,000 without regular additives....but is part guess because many owners never keep the truck that long.

Additives may help, but not necessarily needed.... but I wouldn't use anything but a top couple.... not tranny fluid.
 
ATF is an excellent cleaner. We also used it for years to dissolve internal engine carbon deposits. Probably can’t hurt anything and might help keep your injectors clean. If it makes you feel better it’s worth the effort. :)
 
Lou_tribal said:
Question is would you have got 120K miles without doing this?

L
Click to expand...

LOL kind of difficult to answer a hypothetical, but I trust my mechanic and he uses the ATF fluid in his nearly identical truck, and we both work them pretty hard pulling trailers, etc. I think his reasoning is the lowered quality of diesel today causing injectors to clog and pumps to fail.
 
Seems to me if this is a beneficial practice there would be lots of chatter from satisfied folks. Following to learn.
 
Some folks have been mixing two stroke oil also for a long time since the removal of lubricity in diesel..>>>Dan
 
Porchhound said:


When I purchased my Chevy 2500 (used) my mechanic advised putting a cheap quart of transmission fluid with every 20gal of fuel during fill-up. Since then I've put 120K miles on the truck with no injector issues. Does this process make sense in a marinized diesel environment?
Click to expand...
I don't know if it makes sense but I do know that the fact that you have had no problems in 120,000 miles means absolutely nothing. You would be better off using a lubricity improver rather than following some shade-tree mechanic's ignorant advice.
 
It's not being used for lubricity but for its detergent properties. Fairly common practice amongst the so called "ignorant shade tree mechanics" as well as the 2 stroke oil for lubricity.
 
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I don't think it's that common, but when I've mentioned it to different mechanics they seem to agree additives are beneficial today. I'll just keep doing it, probably out of habit at this time. Truck has a total of 155k, small potatoes for a diesel, but I hope to keep it running for at least another eleven years.
 
I hadn't heard about the two-stroke oil, but makes sense today.
 
Hi,

if it would be good for a diesel engine, then i would think this information can be found in the manuals, i will just find there "do not add additives" to the oil or fuel.

Hard to believe that Cummins would instruct you to shorten engine life.

Here, the fuel is at least additive lubricated by the injection pump / nozzles, hard to believe you wouldn’t have this in the US.

NBs
 
Porchhound said:

When I purchased my Chevy 2500 (used) my mechanic advised putting a cheap quart of transmission fluid with every 20gal of fuel during fill-up. Since then I've put 120K miles on the truck with no injector issues. Does this process make sense in a marinized diesel environment?
Click to expand...

I now have 517,000 miles on my Dodge pickup with a Cummins 6BT 220 HP engine. Never used any additives. It would be interesting to know the history of diesel fuel formulation over the last 50 years. While most are aware of the removal of sulfur which acts as a lubricant, it would be interesting to know what other properties have changed. You have to wonder what other changes were made to be compatible with tier 3 and 4 diesel engines.

The other thought regarding adding ATF to the fuel is whether that effects other things in the fuel formulation. While I can respect a mechanic, I'd rather have someone do the science to see how it effects diesel from tank, through the engine, and out the exhaust.

Ted
 
Porchhound said:

When I purchased my Chevy 2500 (used) my mechanic advised putting a cheap quart of transmission fluid with every 20gal of fuel during fill-up. Since then I've put 120K miles on the truck with no injector issues. Does this process make sense in a marinized diesel environment?
Click to expand...

I would be more inclined to take advice (if at all) from a commercial semi-truck fleet manager. They typically maintain detailed records, take oil samples and if they are finding the use of additives is beneficial I would be intrigued. I personally would not add anything to my fuel based on solitary or anecdotal recommendations here or elsewhere, rebuilds are too expensive.

On another note, a well maintained diesel is likely to outlive any recreational user's usage.

~A
 
North Baltic sea said:
Hi,

if it would be good for a diesel engine, then i would think this information can be found in the manuals, i will just find there "do not add additives" to the oil or fuel.

Hard to believe that Cummins would instruct you to shorten engine life.

Here, the fuel is at least additive lubricated by the injection pump / nozzles, hard to believe you wouldn’t have this in the US.

NBs
Click to expand...

Manufacturers of engines seem to always warn against additives, irrespective of changes in fuel quality because they can't control what you may introduce to your equipment. Besides, they love to void their warranty exposure whenever possible. Low sulfur diesel is bad for engines. Unleaded gas with ethanol is destructive to small engines, yet garden tractors/mowers, etc all warn against using lead additives or alternative fuels (I use leaded gas). The local small engine repair shop recommended it.

The "shade-tree mechanic" I use has kept cars and trucks and farm equipment running in this agriculture community for over forty years. He knows what current fuels do to engines. If he uses ATF in his personal vehicle, I'll call that good.

My question had more to do with diesel engines operating in a marine environment. These old marinized tractor engines, like i have, weren't designed to operate on low-sulfur, low lubricity fuels. Maybe the new diesels are.

The only "additive" system I know of on a diesel here in the states is the DEF where ionized water and urea are sprayed into the exhaust system to cut down on pollution. Owners hate it...just another system to have to monitor.
 
OK - here's a little bit of hijack... but along the same lines regarding an additive:

For older gasoline engines: It is good to add 4 oz. ZDDP at each oil change [actually, I also put in an extra 4 oz. mid way between changes].

Reason - Older gassers need zinc in their oil as a barrier-film between bushings... ya know... flat tappets to cam shaft lobes and the like. https://en.wikipedia.org/wiki/Zinc_dithiophosphate

Anyway... I've currently got five pre catalytic-converter V-8's in different rigs. They all run sweet and use no oil. One 1967 430 ci 360 hp., two 1977 350 ci 255 hp., one 1985 350 ci 325 hp. and a 1996 454 ci 300 hp.
 
Find out what some of the long-haul truckers are adding if anything. That's where the real pay-off and experience is.
 
AlanT said:
I would be more inclined to take advice (if at all) from a commercial semi-truck fleet manager. They typically maintain detailed records, take oil samples and if they are finding the use of additives is beneficial I would be intrigued. I personally would not add anything to my fuel based on solitary or anecdotal recommendations here or elsewhere, rebuilds are too expensive.

On another note, a well maintained diesel is likely to outlive any recreational user's usage.

~A
Click to expand...

Over-the-road trucks use D2, a very different type of diesel which is less volatile. I'd be curious how that affects their engines. I know they get better fuel economy with it.
 
Porchhound said:
I think his reasoning is the lowered quality of diesel today causing injectors to clog and pumps to fail.
Click to expand...

Where does this come from? My filter changing has evolved over the years from twice annually, to every 4 years or so, on primaries and from annual to every 10 or so on secondaries. I have not had any clogged injectors or failed pumps, ever. This convinces me that today's fuel is much better quality than what we put into our boats 25 years ago. I thank the EPA regs, mandating that higher quality, to eliminate most of the sulpher and along with it, most impurities.
 
One of the potential issues I see is the amount of time diesel remains (goes unused) in many small trawlers where our boating season is 3-4 months instead of our southern brothers who get 10+ months of use. In three months in the PNW I expect to make 6 or so ten day trips. I don't think I'l use up nearly 300 gallons at 2 gal/hr. Plus I'll be leaving the tanks full when I put her up for the season. What will the additive do during that 9 months in the tanks?

Hopefully someone on here will know.
 
koliver said:
Where does this come from? My filter changing has evolved over the years from twice annually, to every 4 years or so, on primaries and from annual to every 10 or so on secondaries. I have not had any clogged injectors or failed pumps, ever. This convinces me that today's fuel is much better quality than what we put into our boats 25 years ago. I thank the EPA regs, mandating that higher quality, to eliminate most of the sulpher and along with it, most impurities.
Click to expand...

I haven't seen any references to fuel quality improving over the past two decades other than emissions. Even Cummins is now recommending two additives due to the poor quality of diesel (see above link to Canadian trucker article).
 
I would not add atf unless you are also thinking of adding gasoline
 
Porchhound said:
Manufacturers of engines seem to always warn against additives, irrespective of changes in fuel quality because they can't control what you may introduce to your equipment. Besides, they love to void their warranty exposure whenever possible. Low sulfur diesel is bad for engines. Unleaded gas with ethanol is destructive to small engines, yet garden tractors/mowers, etc all warn against using lead additives or alternative fuels (I use leaded gas). The local small engine repair shop recommended it.

The "shade-tree mechanic" I use has kept cars and trucks and farm equipment running in this agriculture community for over forty years. He knows what current fuels do to engines. If he uses ATF in his personal vehicle, I'll call that good.

My question had more to do with diesel engines operating in a marine environment. These old marinized tractor engines, like i have, weren't designed to operate on low-sulfur, low lubricity fuels. Maybe the new diesels are.

The only "additive" system I know of on a diesel here in the states is the DEF where ionized water and urea are sprayed into the exhaust system to cut down on pollution. Owners hate it...just another system to have to monitor.
Click to expand...

I know CAT says if you need an additive use one that brings the fuel back into specs for the engine...so some manufacturers get it. They sure don't say use tranny fluid though.

As far as over the road truckers using different diesel... I used to get mine from a suppliers truck who also delivered to road stations as well as marinas.... it was also delivered as home heating oil. So while some truckers use different diesel...certainly not all or in all parts of the globe.

Sounds like your minds made up..so go for it. Hey...what could go wrong?.... despite it's neither recommended by engine manufacturers or petroleum organizations or by any fleet managers/commercial vessel fleets I ever knew or read about.

You asked the question...now you want to argue with the half that thinks it's a bad idea and follow the "it's what I do" or "can't hurt" crowd.
 
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I'm not arguing with anyone. I'm asking a question and posting information I've found regarding additives. There is now no question that additives are a good idea for today's low sulfur diesel, with CAT and Cummins recommending them. The ATF acts as a detergent, but it may not be the best route, especially in a marine environment.

That was the original question.

What have we learned in this discussion?
More than half of those who responded didn't know using additives was a good idea. Only one or two knew long-haul truckers use additives (even in Canada), and one person believes that diesel quality has improved over the past two decades, at least in impurities and emissions.

I'd say it was a successful discussion-not an argument.
 
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 In addition, commercially available fuel additives are not necessary for the proper operation of your Cummins® diesel engine

As an FYI, the above was copied from my 2021 Ram owner's manual.
 
That is interesting, thanks. I wonder what they've done to the new Cummins to solve the diesel fuel issue? Someone above mentioned some type of injector on his engine. I tracked down a man who has a small truck fleet and asked about additives, ATF in particular. He said they use them in his trucks (not ATF). ATF is considered old school and cheaper. It probably doesn't contain the lubricant qualities of fuel additives. The Canadian article I posted above listed a couple additives approved by Cummins (not necessarily recommended) which wouldn't void the warranty. Of course we are taking very different uses, commercial big rigs vs what we drive.
 
Porchhound said:
I'm not arguing with anyone. I'm asking a question and posting information I've found regarding additives. There is now no question that additives are a good idea for today's low sulfur diesel, with CAT and Cummins recommending them. The ATF acts as a detergent, but it may not be the best route, especially in a marine environment.

That was the original question.

What have we learned in this discussion?
More than half of those who responded didn't know using additives was a good idea. Only one or two knew long-haul truckers use additives (even in Canada), and one person believes that diesel quality has improved over the past two decades, at least in impurities and emissions.

I'd say it was a successful discussion-not an argument.
Click to expand...

Last thing I read from CAT was use them if your fuel needs them, not a blanket statement that they are needed.

ATF may have detergent qualities but what research has been done to show whether or not it has one or more harmful qualities?

From post numbr 1.... (adding ATF)....." Does this process make sense in a marinized diesel environment?"
 
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