May 19, 2022

Gasoline Vs Diesel Generators

If you’ve decided on a liquid-fueled internal combustion power generator, your next decision is whether to get a diesel or gasoline fueled generator. There are pros and cons to both types. But first, let’s learn what these terms mean, and what makes these engines different.

Gasoline and diesel are both liquid fuels made from refined crude oil. Diesel is less volatile and flammable than gasoline, but contains more energy. Both types of engine use internal combustion – the generation of a series of small explosions or combustions, but the engines operate differently.


Diesel engines tend to be more expensive than gasoline models. Diesel fuel is also more expensive than gasoline per gallon. As of this writing, regular grade gasoline is going for $4.19 a gallon (national average) and diesel fuel is selling for an average cost of $5.09. There are seasonal variations on this price difference but gasoline is consistently cheaper.

Part of this price difference is due to the higher costs of refining diesel fuel compared to gasoline, and part of it is due to high global demand for diesel fuel. (In many parts of Europe, a majority of vehicles use diesel fuel instead of petrol, aka gasoline.) The price of diesel fuel increased in recent decades due to requirements for refineries to reduce the sulfur level in the fuel, as high amounts of environmental sulfur poses various health risks.

Despite this higher price at the pump, diesel is a more efficient fuel to burn, so you need fewer gallons of it to generate the same amount of power. Also, diesel engines have lower maintenance costs (and a longer lifespan on average) because they have fewer working parts. That’s due to the fundamental difference in how these engines operate.


Both engines use a four stroke combustion cycle:

  1. Intake stroke: The intake valve opens up, pulling air in and moving the piston down.
  2. Compression stroke: The piston moves back up and compresses the air.
  3. Combustion stroke: As the piston reaches the top, fuel is injected at just the right moment and ignited, which forces the piston back down.
  4. Exhaust stroke: The piston moves back up to the top, pushing the exhaust generated from the combustion out of the exhaust valve.

Gasoline engines have carburetors and spark plugs which combine fuel and air to create an ignition, which spins the machine’s rotor to generate an electric current that powers the generator. In a diesel engine, the air is compressed first, and then the fuel is injected. Because air heats up when it’s compressed, the fuel ignites.


Gasoline engines are smaller on average than diesel engines. You can see this in the transportation world, as trains, tractors, construction vehicles and buses use diesel fuels, and motorcycles and small cars use gasoline. This size difference means that gasoline generators are more portable. Diesel is a much more common fuel in more powerful, larger, permanently attached generators.


Since gasoline is the most popular fuel in the United States, it is easier to find compared to diesel fuel. But for this very reason, if there is a hurricane coming, or some other event is spiking demand for gasoline, there may be a shortage of gasoline. In these situations diesel may be easier to find. This is notable because these extreme events are what lead people to using a power generator. To prepare for these events, you may be tempted to buy gasoline to store on site, but gasoline doesn’t last very long in storage unless you have special storage facilities.


Years ago, diesel engines had a reputation of being annoyingly loud. This was a major concern for consumers of home backup power generators, who don’t want to annoy their neighbors (or themselves) with loud noise every time they run their generator. Fortunately diesel engines have improved a lot over the years, and models are available, especially from top companies such as Generac, that run very quietly. This is partly from engine innovations but also from the materials and design of the generator’s housing, and how they’re installed.

Despite these improvements, diesel generators are still louder than gasoline models, but they create less heat than gasoline models, which can be a concern in hot climates. The increased heat from a gasoline generator next to your house or equipment may be a safety concern. Diesel generators from Generac and other manufacturers are often liquid-cooled. Seidel Electric Inc. helps home and business owners throughout the Blairstown, New Jersey area with advanced electrical solutions. Whether you need generator repair or want to install a new unit, our qualified technicians will arrive to offer friendly and professional support. Contact our team today to learn more about our services and financing options.