Using used deep fryer grease as motor oil

On my on-again, off-again project vehicle (a postal jeep with an Olds 5.7 diesel) I have modified the fuel system to run on used deep fryer grease as fuel.

I had the bright Idea of tapping directly into the pressurized lube system and using that oil for fuel, so…

How lubricating is used deep fryer grease as a sump oil?

Note: the oil is not kept in the sump for weeks or months at a time like regular motor oil, but is constantly turned over with fresh grease as it is consumed.

Just saw last week’s episode of the TV show “30 days” and they went to a hippie communue – er, experiment in natural energy commune – called the Dancing Rabbit where they had cars that run on biodiesel until the tank temperature hits 100 degrees, at which point they switch to veggie oil, which they get from frying grease.

Can’t answer your question, but I found the idea fascinating!

Burning biodiesel and/or fryer waste oil in a diesel engine is one thing.
Using either one as a lubricant for bearings, pistons/rings is quite something else. They do not have the film strength nor the additives used in motor oil to minimize wear and corrosion.
The will lubricate in an emergency if it is a case of absolute necessity but don’t expect to run long under those conditions.

One of my hippie environmentalist activist Witch friends goes around converting engines to greasel. He said it’s a fairly easy thing to do, mechanically.

doesn’t have the film strength or the additives to allow a modern engine to last under any kind of a load.

…And it will burn up (coke) pretty quickly as well.

Tangentially related:

Therefore, there were early attempts to superheat the steam. With low-pressure, low-temperature saturated steam, the steam temperature could be raised quite a bit with success. But as boiler pressures got higher, with the search for greater efficiency, as metals and designs improved, the superheated steam got too hot and the engines failed.
The problem was not that the metals of the boilers, superheaters, and engines could not stand the temperature. The problem was lubrication. As long as engines were lubricated with animal fat (tallow), temperatures were limited to what the tallow would stand. Get it too hot, and it turned to gritty clinker and scored the valve surfaces so they leaked.


Now, you’re talking vegetable oil rather than tallow, and if I read the OP correctly you may be talking about once-through-and-out lubrication. So there is a chance, just a chance, that this could work in a purpose-designed engine. As a retrofit I’m a bit dubious, partly because of the high starting viscosity.

I’d also worry about forming epoxy deposits on the hot cylinder walls below your piston rings. You might be able to burn these off if they form above the rings due to vegetable oil fuel, but I’m not so sure about formation below the rings due to vegetable oil lubricant. That said, castor oil was used as a lubricant in the WW1 gnome radial aero engine, on a once-through cycle, but it has a lower iodine value than say rapeseed or sunflower oil.

Interesting idea though. If you try it, be sure to let us know how you get on!

Also, with used fryer grease (as mentioned in the OP) you would end up with major deposits in the engine. Used fryer oil is black because of the burnt food particles suspended in it.

It’s filtered first, obviously. Otherwise it wouldn’t be any good as fuel, either.