Inspired by a couple of episodes of The Amazing Race in which people out unleaded gas in a diesel vehicle and hilarity and stalling ensue. What’s so different about diesel that it can’t be used interchangeably with regular or unleaded gas? What’s different about a diesel engine that it can’t burn non-diesel fuel? Bear in mind I know almost nothing about automobiles (I drove my current car for a year before I realized that Drive and 3rd weren’t the same gear…shut up) so a very non-technical explanation would be most appreciated.
I guess no one really does read these, Jenny.
“Can I use diesel fuel instead of regular gas?”
That’s self-effacing humor. I know lots of people read the Staff Reports. Figured I’d better post again before people thought I was looking for attention. 
Ahh, the good old days.
Shit, I’m only 24, and I remember filling up my truck when gas was 99 cents. I just loved watching the “gallons” meter go up faster than the “sale” meter.
With that name, you should certainly know something at least about gas engines. Check out the Otto cycle
Can some larger engines (e.g. piston engines found in tanks) take basically any sort of liquid fuel as long as it ignites under strong compression? Is the term diesel engine used to describe this or solely an engine that uses diesel oil fuel.
IS there a reason that diesel can’t be used in a otto cycle engine (spark ignition 4 stroke), and gasoline can’t be used in a diesel cycle engine (compression ignition), designed for this fuel.
A gas engine has a compression ratio of about 10 to 1. A diesel engine has a compression ratio of about 23 to 1. if you put super high compression pistions in a gas engine to try and make a diesel, you would blow something apart. Either the head gasket, or fracture a cylinder wall. Gas engine designers don’t build that kind of safety margin into their designs. Not nessary, and expensive. General Motors tried to adapt a gas motor into a diesel back in the eighties. Those things broke and blew up like you would not believe.
It was ugly, very ugly.
as far as just pouring diesel into a gas engine, it won’t ignite even when compressed 10 to 1. Diesel is very hard to get burning. The plug won’t ignite it, and after a couple of cycles, the plugs are coated with diesel and will no longer fire. At this point it you have to drain the fuel tank, fuel lines, clean or replace the spark plugs. After running some gas through the system you then replace the fuel filter.
As far as gas in a diesel, putting a tank full of gas into a diesel could really screw up the engine, but in my experience the engine dies, and will not restart. On the cars I have seen this happen to, the engine died, we drained the tank, changed the fuel filter, and gravity fed the pump with clean diesel and got the engine running again. while I agree you could damage the hell out of a pump or engine, the ones I have seen in my repair stall had no lasting damage.
Some older farm tractors were set up for dual fuel use. They would start on gasoline and when fully warmed up would be switched to kerosene by the turn of a valve. They had carbs and sparkplugs, no fuel injectors. I’ve seen these units on display, but never seen one actually run.
Perhaps Una could shed more light on these contraptions?
There was a piece in the Guardian not too long ago about people putting petrol in a modern diesel car by mistake and writing the engine off by the act of unlocking their doors. I can’t find the article on their website, but it was to do with the remote control car key priming the fuel pump when the doors were unlocked (??). The construction of some modern diesel fuel pumps will not tolerate petrol at all, apparently. I’ll see if I can find the piece.
Here it is, in the Telegraph, not the Guardian. Interesting article. This would definitely happen to me if I owned a diesel, I’m too absent minded.
Note that there are diesel cycle airplane engines that run on jet fuel.
Most piston engine planes run on 100LL. LL meaning low laed – though IIRC it has mre lead than old leaded auto gas.
Brian
What would be nice is if they would make available a diesel blend that didn’t stink.
They exist, and I’m thinking they could be used for cars rather than trucks. Cars fill at different pumps after all, so that’s not the issue. But cars release exhaust at street level instead of high up, so they really make the drivers behind them sick.
Right. Diesel pretty much equates to ‘compression ignition’ - no particular kind of fuel is required to qualify as a diesel. (By contrast, the Otto cycle is spark-ignition.)
“Low-lead” is indeed misleading here - it has about 4 times the lead that regular leaded gas used to contain.
I’m afraid not, Gary, those are outside of my experience.
Except that gas wasn’t 99 cents, it was 99.99 cents. 
It’s near imposible to put diesel in a car designed for unleaded gas. The hole for the spigot on the gas tank is too small.
Unleaded gas nozzels at the pump are small and fit into the gas tank filler tube. A diesel nozzel, being bigger will not.
I think it was originaly designed this way to prevent people from putting leaded gas in unleaded cars. Works now for diesel.
You could do it with a funnel I suppose. Or transfer it out of a fuel can. I have both a diesel tractor and a gas plow truck that I buy gas for in 5 gal cans. The diesel fuel can has a big piece of duct tape on the handle. But, you can tell the difference easy between the two fuels. The duct tape is there to prevent me from being a bit absent minded. And to keep me from putting gas in the diesel can and visa versa.
I was hoping that someone else would find it ironic that someone named Otto was asking a question of this nature.
That is not the case in the UK and the rest of Europe. The nozzles and filler tubes are the same size on both diesel / petrol cars and pumps , and are interchangable.This is probably because of the very high number of diesel cars over here. I have personal experience of this, I once put petrol into a diesel car and cost £100 to get the tank flushed out! At some filling stations you do get “truck only” pumps. They do have a larger filling nozzle, and the pumps seem to deliver the fuel at a faster rate.
GaryM, you are basically correct about the dual fuel farm tractors. Many older tractors from the 1920s to the 1950s were made to burn kerosene (similar fuels/names were distillate, parrafin, power fuel, and even light CRUDE oil). You can even burn diesel and home heating oil (about the same thing)
These “all fuel” engines were usually low compression (about 4:1, most gasoline engines were/are 8:1) This is to avoid knocking or pinging. Also makes for easier hand starting if need be. The intake and exhaust manifolds were also nestled together so the incoming air/fuel mix could be preheated. Yes they used a carburetor and sparkplugs, not injectors.
The tractor would have two fuel tanks, a larger kerosene tank, and a small “Starting” tank for gasoline. The tractor is started on gas, and allowed to warm up (usually using adjustable shutters or curtains over the radiator). Once warm, you would move a fuel valve to switch to kerosene. You HAD to keep the engine HOT as kerosene is hard to burn, usually 180 degrees plus, 200 degrees or more is better as long as you aren’t boiling. This required use of the mentioned shutters and by keeping the tractor working hard. Sometimes under a very heavy load the engine would pre-ignite (knock). Some had operator adjustable ignition timing, some also had water injection (basically water was dripped into the carb!) to stop the knocking.
At the end of the day, the engine would be switched back to gasoline and run for a few minutes to get all the kerosene out of the lines/carb. If the engine stalled or was stopped for some reason on kerosene, you had a BIG problem as it was nearly impossible to start on kerosene. You’d end up draining the carb, turning on the gas, and cranking for QUITE a while.
Why go to all the trouble of using kerosene? An engine setup for kerosene would make less power than one that was properly set up for gasoline (i.e. higher compression pistons). BUT it was VERY cheap fuel at the time-You could save alot of money over the course of a year burning kerosene vs gasoline. But eventually the poularity of kerosene ended as gasoline refinerys got better and farmers started needing more power. Most manufacturers stopped offering “all fuel” tractors by 1960.
I actually don’t have much personal experience burning kerosene. My granpa does! In our all fuel John Deeres (and one McCormick), I just use gasoline all the time (it works just fine with no modifications). One time we mixed a little diesel in the gas- it ran OK, smoked a lot-BUT it wasn’t warm enough either.
You can find lots of “all fuel” engines and tractors running and working in your area-just go to an antique tractor show in the spring/summer/fall. Yes, collecting old tractor is a hobby, much like cars. But most of us aren’t afraid to get the tractors dirty and go to work with them!
You haven’t had fun till you’ve hand started a tractor, and rode on steel wheels, while sitting on a steel seat! Did I say F-U-N? I meant O-U-C-H. Nah, still fun!
WeirdDeere
More info on the old tractors Yesterday’s Tractors Magazine website
A John Deere Specific Site JohnnyPopper.com