two questions about diesel engines

[Alpo]

Question one - will a diesel engine run on cooking oil? Not "biodiesel", which, as I understand it, is used cooking oil that they do something to to make it where it will burn in a diesel engine. I don't know what they do to it, but it's like crude oil out of the ground. You can't just burn that in your diesel engine. You have to do something to it to turn it into fuel the diesel will burn. That's what biodiesel is - they take the used cooking oil and do something to it to turn it into a fuel. But my question is, if I took a bottle of Wesson oil and poured it in the tank of my diesel engine would it work?

 

Question number two. My diesel engine has been sitting since the 50s. Bone dry.

 

Now if that was a gasoline engine - assuming that the fuel pump still worked - I could pour gasoline in the tank and then pour a little bit in the carburetor and that would get the engine to start and hopefully the fuel pumps would bring gas up from the tank into the carburetor and I could drive away. But a diesel ain't got no carburetor. So if the diesel is absolutely bone dry, can you start it easily?

 

I remember being told one time that if you ran a diesel bone dry you had that kind of disassemble something to get fuel into the engine to start it.

 

This was a television show, and as we all know television shows are made up, and again as we all know you can do anything you want to on a television show.

 

They had a diesel automobile that had not been running since the 1950s, and they poured some cooking oil - brand new fresh cooking oil - end of the fuel tank and fired it up and drove away.

 

I just wanted to know if that would be possible. If they could fire it up like that, and if it would run on that brand new cooking oil?

 

Personally I don't believe either of them. But I don't have experience with diesels so --- would it?

[El Chapo]

The original Diesel engine ran on peanut oil.  Yes, that is possible.  Diesel engines will even run on their own motor oil.  Go to youtube and put in "runaway diesel engine." 

[Subdeacon Joe]

Digging WAY BACK into the little Grey Cells, vegetable oil is much thicker than diesel fuel. But,  if you put in a system to heat it to thin it out so the fuel system can handle it,  it will run.  Maybe not well, and there will be horrendous carbon build up.

 

I think that you just need to bleed the air and prime it.

[El Chapo]

2 minutes ago, Subdeacon Joe said:

Digging WAY BACK into the little Grey Cells, vegetable oil is much thicker than diesel fuel. But,  if you put in a system to heat it to thin it out so the fuel system can handle it,  it will run.  Maybe not well, and there will be horrendous carbon build up.

 

I think that you just need to bleed the air and prime it.

 

New injection systems may not like a more viscous fuel, but certainly diesel engines will run on all forms of oil if it is injected correctly, which older diesels will absolutely do.

 

Ships routinely run on an oil that is so thick it has to be heated even to pump through a large pipe.

[John Kloehr]

1 minute ago, Subdeacon Joe said:

Digging WAY BACK into the little Grey Cells, vegetable oil is much thicker than diesel fuel. But,  if you put in a system to heat it to thin it out so the fuel system can handle it,  it will run.  Maybe not well, and there will be horrendous carbon build up.

 

I think that you just need to bleed the air and prime it.

Pretty much this. The engine will run on veggie oil, and used cooking oil needs filtering but is otherwise the same as a fuel. For the reasons stated, preheating veggie oil or mixing with diesel (bio-diesel) to get a lower viscosity works better and runs cleaner.

 

Priming a dry diesel engine is a pain. This often involves loosening fittings for each injector to get the air out.

 

Side observation... Some years ago some group did a study to look at the potential profit available converting from fossil fuel to veggie oil. Considering a typical interstate highway and counting passing trucks, they calculated a corn field 6 kilometers wide for the entire length of the highway would support the traffic in the direction they observed. Since trucks need to do a round trip, another 6 kilometers on the other side of the highway is also required. After duly considering these sobering findings, the scientists determined there is just not enough farm land to do this and still grow food for people.

 

The best option would really be to use old cooking oil, filter it, and blend it into fossil diesel as biofuel. Turning trash into a resource. To the extent we have enough Canola oil for food needs, any extra can also reasonably go to biofuel. There is really no other viable crop to grow in the farmable northern parts of Canada. "Canola" is a marketing name as consumers did not like the sound of "rape seed." Growing corn for biofuel is kind of dumb. This "fuel" corn is not the same corn we eat, it is grown only for the oil. The argument to use this land for food crops carries a lot of weight, just not the same subsidies for farmers.

[Subdeacon Joe]

7 minutes ago, El Chapo said:

 

New injection systems may not like a more viscous fuel, but certainly diesel engines will run on all forms of oil if it is injected correctly, which older diesels will absolutely do.

 

Ships routinely run on an oil that is so thick it has to be heated even to pump through a large pipe.

 

Thanks.  Last diesel that I started some 40 years ago was a '50s or early '60s vintage.

 

I guess maybe the technology changed just a little since then.

[Blackwater 53393]

Diesel engines will run on nearly ANY flammable liquid and most flammable gasses if properly metered.

 

Working on agricultural and “over the road” diesels for many years, I learned a few tricks for starting the engines that had been “run dry” as in out of fuel.

 

Those with mechanical injectors can be easily started without “bleeding” the air from injector lines. Simply fill the fuel tank and then take gasoline and spray some into the aie intake while cranking the engine. It will run on the gasoline fumes until the fuel is present in the injectors. At that point, the engine will run as it was designed.

 

”POP” style injection systems present the problem of bleeding the fuel delivery system and injector lines. Opening each connecting fitting in the fuel system, starting with the delivery pump and progressing to the injectors will do the job.

 

I HAVE seen these engines started successfully by applying low air pressure to the fuel tank and cranking the engine while, again, supplying the air intake with gasoline fumes.  They will generally start and run this way, but they usually require SOME bleeding of the system downstream of the distribution pump.  Since the injectors operate on pressure supplied by the distribution pump, air compresses and won’t pass easily through the injectors, while liquid fuel won’t compress! The trapped air causes the engine to run poorly and rough if it gets started. The pressurized fuel tank trick forces fuel at a higher pressure and will usually overcome the air pockets, so once the engine is running, bleeding the individual injector lines gets the last of the air out and allows the system to work properly.

 

Edited November 7, 2025 by Blackwater 53393

[Alpo]

So, theoretically this would work, but not like it did in the TV show. Not just pour a bottle of corn oil in the fuel tank and fire it up and drive off.

[Abilene Slim SASS 81783]

A friend used to collect cooking oil from fast food restaurants for his diesel truck, which needed to be filtered to remove all the gunk from the cooking process like batter and bits of food. He did it with a hand crank device into a big drum, which was really tedious. It was fun for awhile as long as restaurants gave away the used oil, but when they sniffed a buck or two could be made and started charging for it, he quit. Too much work. 
 

He mentioned a conversion process necessary for the truck, which may have been a heater for thinning it. I don’t remember. Whatever the conversion was, he could turn it off or on to run regular diesel or cooking oil. The cooking oil had a separate tank he had put in the bed of the truck. 
 

Edited November 8, 2025 by Abilene Slim SASS 81783

[El Chapo]

On 11/7/2025 at 5:15 PM, Alpo said:

So, theoretically this would work, but not like it did in the TV show. Not just pour a bottle of corn oil in the fuel tank and fire it up and drive off.

 

That would work fine for the vast majority, if not all diesel engines.

 

Modern engines have electric injectors that bleed themselves.  I have to do it every time I change my fuel filter.  Hit the key a few times, fill the housing, start it up, sometimes it dies once, and after that, start it up again and let it run for 15 seconds and it's done.  

 

I certainly have friends who pour their used motor oil right in the tank every time they change their oil.  I don't do it with mine because the injectors are expensive and I don't see the need, but for my friends who have even slightly older trucks, they've been pouring the 3 gallons of used oil in their tank with whatever other diesel is in there without any noticeable difference.  It'd probably be harmless for mine, I've just never done it.

[Marshal Mo Hare, SASS #45984]

Carburetor?  Haven’t had one for years.

 

ran out of gas once and knew I was a mile or so from a station so I put 4 bottles of dry gas in the tank and drove off

[Alpo]

On 11/7/2025 at 3:16 PM, Alpo said:

Question number two. My diesel engine has been sitting since the 50s. Bone dry.

 

Now if that was a gasoline engine - assuming that the fuel pump still worked - I could pour gasoline in the tank and then pour a little bit in the carburetor

 

2 hours ago, Marshal Mo Hare, SASS #45984 said:

Carburetor?  Haven’t had one for years.

As you can see from my original post, I was talking about a car from the 50s. 70 something years ago. Most cars from the 50s that had gasoline engines had carburetors. I say most because Chevy made a couple of cars that had fuel injection. I don't know if they were doing it in the 50s but I know they were doing it in the 60s, so maybe. So MOST cars with gasoline engines had carburetors.

 

What automobiles currently have or do not have, has nothing to do with the question, which was about a car from the 50s

[Sedalia Dave]

17 hours ago, El Chapo said:

 

That would work fine for the vast majority, if not all diesel engines.

 

Modern engines have electric injectors that bleed themselves.  I have to do it every time I change my fuel filter.  Hit the key a few times, fill the housing, start it up, sometimes it dies once, and after that, start it up again and let it run for 15 seconds and it's done.  

 

I certainly have friends who pour their used motor oil right in the tank every time they change their oil.  I don't do it with mine because the injectors are expensive and I don't see the need, but for my friends who have even slightly older trucks, they've been pouring the 3 gallons of used oil in their tank with whatever other diesel is in there without any noticeable difference.  It'd probably be harmless for mine, I've just never done it.

 

IMNSHO Pouring dirty engine oil into the fuel tank is not very smart or cost effective. Seems to me that doing that will shorten the life of the fuel filter as it now has to filter out all the contaminates in the oil..

[El Chapo]

1 hour ago, Sedalia Dave said:

 

IMNSHO Pouring dirty engine oil into the fuel tank is not very smart or cost effective. Seems to me that doing that will shorten the life of the fuel filter as it now has to filter out all the contaminates in the oil..

 

I'm pretty sure people with heavy equipment and older diesel engines have been doing it for as long as there have been diesel engines.

 

Fuel filters live a very short life in the diesel world.  I replace mine every year and my truck is basically only used for trips (many of which are cowboy and WB matches).

[Joe LaFives #5481]

I would be concerned about all the gaskets , rubber hoses, and belts being dried out,  is that not a concern?

[El Chapo]

12 minutes ago, Joe LaFives #5481 said:

I would be concerned about all the gaskets , rubber hoses, and belts being dried out,  is that not a concern?

 

I guess it'd be a concern if it just sat forever, but it gets used enough.  It has 110k miles on it over the last 20 years.

[Joe LaFives #5481]

1 minute ago, El Chapo said:

 

I guess it'd be a concern if it just sat forever, but it gets used enough.  It has 110k miles on it over the last 20 years.

I was referring to the OP who said it sat since the 50s.

Edited November 10, 2025 by Joe LaFives #5481

[Matthew Duncan]

On 11/7/2025 at 7:15 PM, Alpo said:

So, theoretically this would work, but not like it did in the TV show. Not just pour a bottle of corn oil in the fuel tank and fire it up and drive off.

Would not work.  Sitting since the 1950s the battery would be dead.