Reader Question: The 100 MPG Carburetor?

Print Friendly, PDF & Email

Here’s the latest reader question, along with my reply!

Shane asks: Do you know anything about or have any opinions about the rumored 100 MPG carburetor? I remember hearing about it as a kid. Thanks!

My reply: I heard about it, too. The theory behind it, apparently, has to do with vaporizing the fuel (as opposed to the largely liquid gas droplets dispensed by a carburetor) so as to greatly increase the energy actually used as opposed to wasted. Fuel injection works on the same general principle; i.e., the gasoline is pressurized to create a mist which is then sprayed into the combustion chamber.

But while the droplets are finer, they are still not quite vapor.

I’m  not sure as to how, exactly, the 100 MPG carburetor vaporized the fuel (which would be in unpressurized liquid form in the carb’s bowl). Maybe someone reading this will chime in . . . ?

What I do know is that fuel economy could be close to 100 MPG with known fuel-delivery technology. The chief reason it’s not is because of weight and the main reason for that is government – the regulations pertaining to “safety.”

Consider a new car such as the Hyundai Accent, which can reach 40 MPG on the highway. This car weighs about 2,700 pounds. What kind of mileage would it be capable of – all else being equal – if it weighed 1,700 pounds?

Probably close to 60 MPG.

But wait. If this car weighed 1,700 pounds rather than 2,700 pounds, it would not need the same size (and output) engine to maintain the same performance. A smaller, less powerful engine would use less gas, bumping the gas mileage up, again.

Now imagine a 1,200 pound car – with an appropriately sized engine. It might not be “safe” – in the government sense, meaning if you crash it into something, you stand a greater chance of being hurt – but it does not mean you will crash, or are more likely to crash.

And it would likely mean 70 or 80 MPG.

Maybe even 100!

. . .

Got a question about cars, bikes, or Sickness Psychosis? Click on the “ask Eric” link and send ’em in! Or email me at if the @!** “ask Eric” button doesn’t work!

If you like what you’ve found here please consider supporting EPautos. 

We depend on you to keep the wheels turning! 

Our donate button is here.

 If you prefer not to use PayPal, our mailing address is:

721 Hummingbird Lane SE
Copper Hill, VA 24079

PS: Get an EPautos magnet or sticker or coaster in return for a $20 or more one-time donation or a $10 or more monthly recurring donation. (Please be sure to tell us you want a magnet or sticker or coaster – and also, provide an address, so we know where to mail the thing!)

My eBook about car buying (new and used) is also available for your favorite price – free! Click here.  If that fails, email me at and I will send you a copy directly!


  1. I have never been able to find one of the carburetor mods, but a US automotive manufacturer had an opposed fuel flow carb that exceeded 50 MPG in heavy late 70s/early 80s model vehicles. The way it worked was with an air pump that was directly opposed to fuel flow just before the fuel went in to the cylinders. The micro-atomized fuel was similar in nature to actual fuel vapor hence the decreased fuel flow. An increase in the size of the radiator is likely required for hot climates because some of the liquid fuel is used to cool the cylinder walls. Anyone with engine technical abilities should be able to figure out how to make one of these modifications and share with the world LOL.

    • To clarify, the modification was not supposed to be released and a few hundred(?) made it off the assembly line by a rogue engineer who believed in the design before the mod was stopped and the company issued a recall to remove the components from all of the vehicles sold. Slim chance there are any vehicles out there, but I think there are mechanics who can reproduce this after a few experiments.

  2. Meanwhile a Tesla owner discovers his (2013) eight year old car is basically garbage when the battery needs to be replaced. 20k to replace the battery. So instead of doing that, blows up the car with dynamite with a dummy of Musk in it.

    So how are electric cars green? Most ICE cars can easily get to 20 years old without a 20k repair.

    • Hi Rich,

      Hilarious – and sad!

      Heck, my 20-year-old truck didn’t cost $20k when it was new. And it certainly hasn’t cost me $20k more. In fact, I could probably sell it right now for $8k, which is a pretty good return on my investment. But I won’t, because it’s a better investment o just keep on driving it. And for another $20k, I could rebuild it to functionally/cosmetically as-new. And it’d be good for another 20-plus years…

  3. I was thinking – is this along the same path that gave us direct injection? The fuel is under much higher pressure and is nearly a vapor when it is injected directly into the cylinder. Not 100 MPG, but it did increase MPG, horsepower, & torque. And as Eric mentioned, remove the extra weight and I wonder what an economy-tuned DI car could get.

  4. As noted, “gasoline” doesn’t burn at all in its liquid form. Gasoline vapor, in the most efficient ratio to oxygen, is explosive and highly dangerous.

    This system was theoretically possibly when it was touted as a conspiracy during the 1970s fuel shortage, but before computerized controls came along it would have amounted to driving a rolling bomb.

  5. I used to know one of the engineers who claimed to have created that carburetor. He showed me the blueprints, and I photographed them.

    The theory is that gasoline engines just run off the high-end turpenes, and the rest is burned in the exhaust, or not at all. (liquids don’t burn, only gasses)

    The device used exhaust heat to boil the gasoline completely before combustion. This is quite tricky. You have to use an electric heater to get it started, then you have to know in advance how much gas is going to be needed, and you have to consense excess vapor and recycle it. He said the prototype got 112mpg (if I remember correctly) in a cadillac, and it took a separate person to anticipate the road conditions and “drive the carburetor”.

    They were marketing it to car manufacturers, and he claims they had good initial response, until they were sued for patent infringement. Apparently this thing was previously invented in the early 1900s, and GM bought the rights. He says he was blacklisted and never able to work again as a chemical engineer, destroyed his marriage and family, lost everything.

    This guy was quite credible, and though destitute when I knew him, is rumoured to have since come into inheretence, and now has a MIG farm in a desert.

    • Patents are good for 17 years with some minor variability. You cannot be sued for infringing on a patent from the early 1900s in the 1930s-1970s when this mythical carb supposedly was around. All that could happen is that you could not get your own patent.

      Also any patents should be findable. There’s no way car manufacturers can blacklist a chemE. A ChemE can work in a wide variety of industries at companies big and small.

      I do recall hearing this heated gasoline concept before though.


Please enter your comment!
Please enter your name here