The Different Types of Diesel Fuel: #1,#2, and #4

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Diesel fuels are broken up into 3 different classes: 1D(#1), 2D(#2) and 4D(#4). The difference between these classes depends on viscosity (the property of a fluid that causes a resistance to the fluid’s flow) and pour point (the temperature at which a fluid will flow).

#4 fuels tend to be used in low-speed engines. #2 fuels are used in warmer weather and are sometimes mixed with #1  fuel to create a competent winter fuel.  #1 fuel is preferred for cold weather as it has a lower viscosity. It used to be standard to see the fuel # on the pump, but a lot of gas stations do not state the fuel number anymore.

Another important factor is the rating of Cetane in the diesel fuel. Cetane is similar to Octane for gasoline fuel and it indicates how easy the fuel will ignite and burn. Since Ultra low Sulfur diesel fuels became standard in the middle 2000s, the cetane has been reduced which makes the newer fuel less desirable for diesel enthusiasts. It is highly recommended to run a fuel additive to increase the overall Cetane number. Diesel fuel additives such as Fuel Bomb will also have lubricity additives which will help the modern diesel engine run better and achieve a higher fuel economy(MPG). One other feature of a diesel fuel additive is that it does not need much per tank. A standard bottle of diesel fuel additive usually treats 250-500 gallons.

Here is an article from Diesel Power Magazine on diesel fuel additives and why they are important.

Synthetic diesel comes from several sources such as wood, straw, corn and even garbage or discarded foods.

Biodiesel is an ecologically-friendly type of diesel. It is a cleaner-burning diesel made from natural, renewable sources such as vegetable oils and animal fats. Biodiesel is helping to reduce American dependence on foreign petroleum. It is also helping in the creation of green jobs and the improvement of our environment.

31 thoughts on “The Different Types of Diesel Fuel: #1,#2, and #4

  1. Pingback: diesel fuel - OIL WORLD 2011 – OIL WORLD 2011
  2. hi, still not clear for me the different of 2D and 4D. You mentioned that 4D used for low speed and 2D for high speed?.
    what the parameter..?”..thanks

  3. I see signs that say truck diesel, car diesel is there a difference and is the truck diesel bad for diesel cars.

    1. I would assume that sign is designed for traffic patterns instead of an actual different type of diesel. There often are pumps that can handle larger vehicles and trucks and so they want those people to use the truck pumps. There should not be a difference between the 2 fuels. There is a possibility that specific fuel stations add in fuel additives that truckers would like. I honestly do not know why they would mention a difference.

    2. One difference I’ve found at fuel stations between “truck diesel” and “car diesel” is the nozzle for the “truck diesel” is too large to correctly fit in my VW Jetta.

      Here is another diesel fuel difference. You can get “off-road” diesel, but that is for farm tractor use, or perhaps grading equipment. It does not have the highway tax added to it. It is dyed red so if you are caught with it in your car or truck driving down the road you will be in trouble.

  4. I would like to know what is the best or type of Deisel to use in my 2014 Thor citation sprinter motor home. Type and product number.

  5. When purchasing fuel I was offered Biodiesel or regular. I responded that I would take “what ever”. I have noticed a lot of rust occurring on fuel caps and main tanks. Is this due to the type of fuel? I am aware of ethanol absorbing moisture in marine applications, could there be an issue here?

  6. will you please help me understand what is D2 500 type of diesel found to be in distribution in the market either bulk supply (wholesale) for redistribution to fuel stations.

    1. You are mostly going to find just the #1 and #2 at your local station. #2 is used typically in warmer climates or weather whereas the #1 is used in colder climates or winter.

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  10. #2 diesel is clearer and foams a lot less than #4 and I know for a fact that the diesel I buy at Kroger is # 4. I wished I could find somebody that did retail #2 diesel in Palestine, Tx. The manufacture of my tractor and my 1 ton pickup recommend using a fuel with less sulpher and the greener the diesel the more sulpher

  11. I appreciate you helping me learn more about the three classes of diesel fuel: 1D, 2D, and 4D. Before reading your article, I thought there was only one type of diesel. I’m actually looking for a diesel fuel delivery service in our town for my dad’s old car. When I find a shop, I’ll make sure to ask for a #4 diesel fuel since it works best for low-speed engines. Thanks.

  12. Use whatever diesel is in the local pump. It’s climatized for the area and season. If you’re in an area that has #2 diesel and you’re immediately heading in to someplace really cold, simply buy some diesel additive and pour in that lowers the pour point. Buy it at a truckstop if you can – they should be able to answer your questions. Don’t worry about #4 diesel. It’s for off highway equipment only and you likely won’t find it unless you go asking around for it. Actually, I’ve never heard of it, so it’s most likely only found in the farming communities. It might work in your car or pickup, but performance will likely be less than stellar.” Car” and “truck” diesel pump island signs only reference the nozzle size. The nozzle for the big trucks is much larger for filling 150 gallon tanks quickly, which have much larger filler necks. It won’t fit in a passenger car or pickup truck. The diesel used in every big truck is identical to diesel used every passenger car and pickup. Off highway/off road diesel is identical to highway diesel and will run just fine in anything that requires diesel – just don’t get caught. There’s no road taxes on it. And it may have more sulfur in it. But that won’t affect the engine, only emissions. Highway diesel is limited to 15PPM sulfur. And there doesn’t seem to be any performance differences from one brand of diesel to another like there can be with gasoline. That should be 99.9999% of everything you need to know.

  13. I am looking to get into semitrailer industry not sure if as a driver or mechanic this information I did not know. It has helped me thank you.

  14. kerosene is #1 diesel and is cleaner burning but lower BTU which is less power output. I can remember when kerosene was 0.10 cents a gallon before the jet age and turbines, things has changed in the last 70 years.

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