What is the Difference Between Diesel and Gasoline?

Gasoline and diesel fuel are the two main sources of energy for today’s cars.  Although they are both derived from the same source (oil) they certainly aren’t interchangeable, have different chemical properties and are burned in two different ways.  Below is a quick overview of the differences between the two fuels and the pros and cons of each.

First off, there are very long winded, scientific answers to this question, and if you’ve come here for that you’re not going to find it.  This is going to be a very quick and dirty breakdown of the two fuels with minimal chemistry and jargon.

Both gasoline and diesel fuel are derivatives of crude oil, however they each consist of very different molecular structures.  This happens due to each fuel being derived at different temperatures within the crude oil refining process.

difference between diesel and gasoline, diesel and gasoline differences, difference between diesel and gasAside from the chemical differences, the diesel fuel and gasoline differ in how they are burned and used to create energy for your car:

Gasoline Engines: Cars that use gasoline have to use spark plugs in order to ignite the fuel, which is due to the fact gasoline engines have a relatively low compression ratio.  Here is what a typical stroke cycle looks like for a gasoline powered engine:

  1. Gasoline and air are combined and forced into the cylinder
  2. Gas/air mixture is compressed.
  3. Spark plug fires causing the mixture to ignite and explode, forcing the piston up and giving your car power.
  4. Burned mixture is forced out as exhaust.

Diesel Engines: Because diesel engines have much higher compression ratios, a diesel engine doesn’t utilize spark plugs.  As I’m sure you remember from chemistry class, as gases are compressed, their temperature will increase, and diesel engines have such a high compression ratio that the heat produced by the compression is enough to ignite the fuel/air mixture.  Here is what the typical stroke cycle looks like for a diesel powered engine:

  1. Air is forced into the cylinder, and is compressed.
  2. As this is going on, diesel fuel is sprayed into the cylinder.
  3. The compression causes the diesel fuel to ignite, causing the piston upwards, which gives the car energy.
  4. Burned mixture forced out as exhaust.

Of the two fuels, diesel tends to get better gas mileage than gasoline because it has a higher density, which leads more energy per each explosion within the cylinder.  Also, diesel engines tend to be more efficient by nature.

Despite the better fuel economy from diesel fuel, gasoline is the cleaner burning of the two, and is one of the main reasons why diesel cars aren’t as popular in the United States.

So, that’s the quick and dirty look at the differences between gasoline and diesel fuel.  If you would like a more in-depth breakdown, there are plenty of resources online that will be able to help you.

Comments

  1. Very interesting article. Thank you.

  2. It is a really useful article. Thanks

  3. Explained in a very simple and easy to understand way. Thanks a lot

  4. wow thanks it maked me understand how my engines works!! ty..

  5. i think it should be more professional

  6. it answered every question i needed

  7. thanks a lot for this quick response…… more power!!

  8. thank you

  9. Anonymous says:

    Thanks for the article!

  10. That was a good explanation. However it wasnt the answer I was looking for. I was looking for more of the description of it. I needed to know the difference in smell, color, I guess consistency. Also, if there was a way to test it out to make sure of the difference.

  11. ooohh

  12. whooa, i did not know that.

  13. ryan monsma says:

    it helped me alot to under stand why diesle is a better fuel.

  14. Great article, thanks! You explained it much easier than my husband ha! But I just saw a commercial ran by audi, and it said to buy their diesel so we don’t have to depend on foreign oil and can send it back? Now I am just as confused, how can that be if they are both (gas,and diesel) derived from oil? Any help would be great if you know. Thanks again!!

    • What they actually mean is that there will be “less” dependence on foreign oil imports if we use a significant fraction of diesel fueled pass cars and such on-highway vehicles (18-wheeled semi market is already dominated by diesel engines). This is mainly because Diesel engines are approximately 30% (relative) more fuel efficient than relevant gasoline engines. More fuel efficiency means, less fuel usage; hence, less crude oil imports eventually. Hope this helps.

  15. Anonymous says:

    very good explanation….
    it is easily to understand…
    TY….

  16. That was pretty good but however i need to know the diffrence in the valves in both engines and which one is a better to be used in racing situations…thanks

  17. thank u

  18. you had an gramer eror you said upward instead of downwards
    hahahahahahahahahahahahah

  19. AngelIsland says:

    That was a very interesting article, breifly informative. What is even more interesting though is jonathan’s need to point out incorrect grammar while using both incorrect spelling and grammar… yes jonathan there are two “m”s in the word “grammar”.

  20. Thanks alot,
    Im doing a report on Diesel engines.
    This was veeeeeeeeery helpfull.
    =D

  21. Not really as detailed as I was looking for but maybe you can answer my questions? Why can gasoline not have as high of compression? If gasoline did have the same high compression could you inject it and it be ignited in the same manner? If it could be done in the same manner which would be more efficient and so on?

  22. Simple is what’s stays in the mind. My brain just go another indent from learning something new. Great work.

  23. Sorry Diesel is cleaner

  24. Very nice and helpfull! thank you very much. I can use this info to my project in the secondary :D

  25. Diesel engines also tend to be much louder, and drivers often leave them running when gas engines would be turned off (e.g., at a drive-in), leading to more noise pollution.

  26. This is just the quick answer I was looking for. Thanks!!!

  27. Diesel is cleaner

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