Mixing fuel and transmission fluid

GregH · October 15, 2010

Recently I purchased a used 2002 F-250.. Got it for a great bargain, and even have a spare engine for it.

I've been thinking of cutting the diesel fuel with filtered used transmission fluid from our flush machine. I've read that people have run varied concentrations with no or few side effects, and I was in class with someone with an older (1993ish) who runs nothing by 100% used ATF.

We are in a non emissions controlled state, and the DOT here doesn't dip non commercial fuel tanks to check for red fuel.. What do you guys think?

Bruce Amacker · October 15, 2010

1. This was common in older mechanical injection engines. With electronic diesels it is not a good idea, the nozzle tip orifices are smaller for better atomization and the heavier viscosity oil won't pass through as well. It's possible to blow the tip off in an extreme case.

2. All mfr's have TSB's out to recommend against this practice for another reason- the top piston ring has much tighter tolerances these days and may stick in the piston from carbon buildup, causing loss of compression. I did see this a while back on a DTEGR engine run on poor quality fuel in the Caribbean with very low miles.

Good Luck!

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Jim Warman · October 15, 2010

What Bruce said. Even as recently as the 70s, we would add a quart of new ATF to a fuel fill in the winter (a fuel fill being 150~200 gallons). Back then, the winter fuel we would buy in northern Alberta wasn't much more than home heating oil in disguise (you could sure tell the power difference) and was, comparatively speaking "dry" when compared to summer fuel.

The two stroke "Disneyland Diesel" engines were often mentioned in anecdotes regarding increased fuel pump and injector life but I don't ever recall seeing anything even approaching a scientific study.

joshbuys · October 15, 2010

I work with a guy here that has been running his 7.3L (2002? IIRC) on a 50/50 mix of fuel/used transmission fluid for several years now with no major issues. He has a filtration system in his garage that runs the used fluid through 2 or 3 filters before pumping it into the truck.

Jim Warman · October 15, 2010

What might be coming out the tailpipe?

Bruce Amacker · October 15, 2010

I work with a guy here that has been running his 7.3L (2002? IIRC) on a 50/50 mix of fuel/used transmission fluid for several years now with no major issues. He has a filtration system in his garage that runs the used fluid through 2 or 3 filters before pumping it into the truck.

I know someone doing it locally here, too, but I still don't recommend it. In my opinion injector life will be shortened considerably due to the cleanliness of the fuel mixture.

As for filters, most people forget one very important fact- you cannot push cold oil through filter paper. Most, if not all, engine oil and ATF goes around the filter through a bypass valve until the oil is warmed up enough to go through the media at a reasonable pressure (the last one I checked was rated at 11psi pressure differential). I don't care how many filters he passes it through, if the bypass valves open up on them all he's wasting his time. There are filters available that don't have bypass valves in them, for use on a system that has a bypass valve mounted in the filter header (i.e. 7.3 PSD, SBC/BBC). In this situation the oil would definitely pass through the media, but if he uses a strong transfer/hydraulic pump it could easily cause a blow-through of the paper element allowing 100% bypass of the filter element.

There's just too much going wrong here for me to support. Can it be done? Yes it can. Will you have problems? Probably. Are the resulting problems cheap? Price out a set of injectors (and pulling the motor for a carbon clean job) and let me know.

Take a look at the homemade biodiesel gang and see how many of them run their "fuel" in electronic diesels. Very few, and there's a reason for that.

Let us know what you do, and good luck! (You're gonna need it)

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Keith Browning · October 15, 2010

I am a firm believer that if it was not designed or intended to be put in the fuel tank then it has no business being there. Shit, there's some stuff that IS intended to be dumped into the fuel system that I would never put there! Just because "they" say you can doesn't mean that you should.

Jim Warman · October 16, 2010

Much like putting asparagus into a can.... just because you CAN do it... it doesn't follow that you SHOULD...

(on reflection.... putting asparagus INTO the can is prolly OkeeDokee - taking it OUT of the can - that's where the trouble starts).

GregH · October 17, 2010

I elected to put 4 gallons of used ATF and then topped off with diesel. So, this is about a 20% mixture. So far, I have seen no drivability differences, and there is no smoke from the tailpipe. Fuel mileage rose slightly from 14.5 to 17 according to the OTC estimate. I'll be starting a second tank of this mix shortly.

Down here in the south, our coldest days just barely cross the freezing mark. This mixture, once homogeneous, still flows well - no visible differences after leaving it in the freezer.

I am emboldened to this venture by the fact I have a spare complete engine for this vehicle. So, if an injector tip blows off, or some other catastrophic event, then I'm out the inconvenience of swapping it out. This is our spare vehicle that I'm putting into temporary full time use...

I'll let you know how it goes...

Oh, and I agree with canned asparagus - as with most canned vegetables. However, Green Giant has this line of sweet corn canned with a minimum of water - very tasty. And Bush's has a line of low sodium black beans that serve very well over scrambled eggs. Add a little salsa and a bit of cheese...

Jim Warman · October 17, 2010

"Low sodium?" Ewwwwww.

Trying desparately to avoid references to a low sodium diet and burning ATF.

On a sidenote, fire fighting has become so much more deadly as years go by because burning things (especially synthetic or man-made compounds) creates new compounds. Depending on the heat of combustion, these "new" compounds can recombine into other "new" compounds - none of which have had much in the way of study.

For years and years we splashed R-12 around like it was water... and today we are still paying for that.

OTOH... I was watching a commercial on TV last night. A new hand soap where you don't have to touch that nasty, germ laden pump plunger on the soap dispenser.... A battery operated, proximity activated soap dispenser. Now... if I could only figure out how to get that nasty, germ laden soap bottle off the store shelf and into my bathroom....

Aaron · October 18, 2010

Green Giant "French Style" cut green beans are pretty good. I'd eat them right outta the can...

Matter of fact... peel the paper label off, open the can, set it on the stove burner for a few minutes... Good to go. Since I don't have any pots and pans left..