Diesel Generator Buying Guides

Diesel Generator Buying Guides

Diesel engines work by compressing air with a piston to create heat necessary to ignite the fuel that is then directly injected into it. The hottest point is when the piston is at top dead center. Fuel injection happens at this point or slightly afterwards. The fuel bursts into flame exploding and pushing the cylinder down again. Most diesel engines are designed to work with the air density we have at 500 feet or less. For every 1000 feet in elevation the air density decreases 2.9 - 3% At 3000 feet there is up to 9% less air to compress so less heat is generated. The loss of heat results in incomplete combustion and loss of power. The incomplete combustion also damages exhaust systems and shortens engine life. Starting your generator is also harder. Turbo systems on larger engines are able to ram more air into the combustion chamber increasing the air density however, portable generators do not use turbo or super chargers. Since we start to notice a difference in performance at 3000 feet we suggest you do not buy a diesel generator. It is not considered normal operating conditions and any engine damage would not be covered. It is the same with all diesels however, most other sellers will not tell you this. For higher altitudes you need a super charger or turbo charger. That is only something you find on larger diesel engines. They are compressors that ram more air into the engine to create higher pressures and greater air density.

What else can you do?

Note that any modifications to your engine may void your warranty. Try the following at your own risk. Advance the fuel injection timing. This will give the fuel more time to burn. How do you do this? The fuel pump is a plunger and barrel that has precise timing. It is controlled by a lobe on the cam shaft that makes contact with the plunger at a specific point pumping fuel under high pressure to the fuel injector and into the engine. If you could move the plunger closer to the lobe on the cam shaft, then it will happen sooner. If you move it away, the contact will be delayed. The fuel pump is mounted to the engine body and has a copper shim / gasket between itself and the engine. If you remove one of the copper shims it will advance the fuel injection timing. This will work up to a point. You may have also effected the amount of fuel being pumped so you may have to adjust the engine throttle to correct the speed. The other thing you can do and it is not tested is simply lower the temperature that it takes to burn the fuel. This can be done by adding a more volatile substance to the diesel fuel. Acetone will work. It will lower the "flash point" of your fuel. Careful because anything you do may damage your engine and or cause you harm!


The flash point is an indication of how easy a chemical may burn. Materials with higher flash points are less flammable or hazardous than chemicals with lower flash points. For example

  • Propane -156 oF
  • Gasoline - 45 oF
  • Acetone 0 oF
  • Diesel Fuel (#1) 100 oF
  • Diesel Fuel (#2) 125 oF
  • Diesel Fuel (#3) 130 oF
  • Kerosine 100-162 oF

Acetone is a product that can be purchased inexpensively in most locations around the world, such as in the common hardware, auto parts, or drug store. Added to the fuel tank in tiny amounts, acetone aids in the vaporization of the gasoline or diesel, increasing fuel efficiency, engine longevity, and performance -- as well as reducing hydrocarbon emissions. Ethanol Alcohol absorbs water it is highly corrosive to steel so it is not a good choice.

How Much to Use

Add in tiny amounts from 1 - 3 oz per 10 gallons. Not more than three oz. per 10 gallons.

What we suggest

Do not buy a diesel generator if you plan on using it above 3000 feet unless it is a turbo diesel and or enough power to overcome losses in power.  Not sure? Just ask us

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