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Waste oil used as additive in older engine?

In older carburated engines, is it possible to run a mixture of waste oil and gasoline? Has anyone tried this?

Doesn’t anyone screen these questions?

No you can’t.


How much smoke do you want to make?? If you can no longer afford to own, operate and maintain a roadworthy vehicle, then do us all a favor and use public transportation…

I hope this is a joke. I understand the desire to find a way to dispose of waste oil, but this ain’t it, and for several reasons. One, adding oil to the gasoline changes it’s burn characteristics, and results in a ‘dirty’ burn, same as if you had bad rings or valve seals. Two, waste oil contains a lot of crud and junk the detergents have picked-up. Changing the oil is how you remove them from the engine, and then you want to put them back in? And through the carburetor to choke it up? And three, this additional crud could even clog up the fuel filter in short order. I could go on, but waste oil needs to be disposed of properly, not put back in a car, any car.

This idea will work as well with a fuel injected engine as it would with a carbureted engine, which is to say it will not do anything but make a lot of smoke and ruin the fuel system.

Wonder if this loopy idea has been tried. :wink:

As a heating tech I had this same question come up. An auto shop owner asked me if he could burn used motor oil in his oil furnace. I told him no seven different ways about how it would make a horrible mess. Of course two days later I went out for a no heat and you know what happened. He ruined the oil pump, plugged all the filters, ruined the nozzle, and plugged the heat exchanger with a weird sticky tarlike substance. His attempt to save $20 cost him over $1000. Of course he denied that he mixed motor oil with his #2 oil. But he had no one else to blame because he also sold heating oil on the side. Days like that make it all worthwhile. jCan you imagine what it would do to an engine with fine tolerances vs a crude old furnace? How much do you want to bet he’s already ruined his car.

When I drove for Yellow Freight in the mid 90s they changed oil in the tractors (48) quarts) and dumped it in the 1230 gallon tanks of that Tractor. They ran lousy and smoked a lot but seemed to suffer no ill effects after they burned up that tankful.

My grandfather had an old oil-burning heater in his garage–basically one of those you used to see in people’s living rooms in old houses that had not been converted to central heat. He often used to dump old motor oil in the kerosene tank that fed it. The tank held about 40 gallons and he would dump only about a gallon of waste oil at a time in there with the K1. This thing had no filters and only a primitive gravity-feed for the fuel system. It seemed to suffer no ill effects and would burn anything combustible, especially once it got rolling and one whole side would glow dull red.

I suspect there was all manner of scary crud accumulated at the bottom of that tank. I would not attempt to use waste oil of this kind in any sort of internal combustion engine, even if you filtered it, any more than burning old plastic and wrapping paper in your wood burning stove in your house. I’m sure you would have an unholy mess distributed throughout your fuel system and in the bottom of your gas tank if you tried.

In addition to laying waste to the fuel system and causing problems in the combustion chambers, if this mystery vehicle has a catalytic converter, this exercise in foolishness will become very expensive very quickly.

Or, to use an old saying…You can’t afford to save this much money.

If you ever shop at a Walmart, they will take the old waste oil off your hands.

Our landfill has a depot for used oil, antfreeze and paint. No charge for dumping it. Check out your town dump.

With respect to mixing it, I would not even put it in a 2 cycle lawnmower engine (which takes an oil/gasoline mix); the oil is too dirty to burn properly.

When I was a farm kid, the county used to spray used oil on the gravel raods for dust control. Even that is now prohibited.

Many places that sell oil, now also take waste oil.

Robert, is that you ?

@Ryanqzqz no offense, but you sound like a real cheapskate.

I hope you don’t also buy used old patched tires.
I sense that you don’t want to let anything go to waste. But . . . sometimes it’s better to properly dispose of something rather than reuse it and possibly ruin something else in the process.

I hope that this guys was kidding. Rocketman

To answer the OP’s question, yes, it’s possible. New oil has been run for many years in two cycle engines. If you filter the oil first and use it in an older car with a carburetor, if something does not go well, you may have little to lose. I can think of three effects from doing this: Air pollution if no cat converter, the engine will get faster carbon depositing on the piston top and combustion chamber in the head. If the used oil is high in ZDDP, it will slowly poison your cat converter. One consequence of excessive carbon deposits is an increased compression ratio that may induce detonation requiring a higher octane fuel at higher expense.

Cummins purposely burns used engine oil in diesels as part of their optional Centinel system. I don’t know what rate they are using oil but if you diluted gasoline and used, filtered oil in a ratio of 160 to 1, your engine should be fine for a long time.

If your engine presently burns no oil, think of it being a car engine that burns one (used) quart of oil per 1000 miles which is designated as normal by some. At an assumed 25 miles per gallon, that would be 40 gallons of gasoline per one quart of oil or a ratio of 160:1 for 1000 miles. Assuming that the oil makes the same power as gasoline, you will get 6.25 extra miles from a quart of oil.

“Doesn’t anyone screen these questions?”

@Tester, you just did. The process works!

If the OP wants to go through the trouble of filtering the oil wouldn’t he be better off putting the oil back in the crankcase and using it again as oil?

If he’s not going to filter it then isn’t be just putting dirty oil in as fuel?

@threephi, filtering is not enough. The engine has a filter. The detergents have collected a bunch of crud and the friction modifiers are used up. The oil needs to be re-refined in order to separate any good oil molecules from the bad and the ugly, then mixed with clean detergent and fresh friction modifiers before going back in the engine. Otherwise, why do an oil change?

If you’re wondering, yes, recycled motor oil certified by API has been available for years.

If the OP wants to go through the trouble of filtering the oil wouldn’t he be better off putting the
oil back in the crankcase and using it again as oil?

Years ago the oil sumps in ocean liner engines would route the oil to a separate room where it was run through centrifuges to remove particular contamination. After that it was routed back to the engine again.
I believe they also did something for the chemical contamination but my memory fades me for exactly what that was.