The farm has a green jerry can that was filled with either gas or diesel last year. I'm not certain from smell alone which it is.

What's a good way to identify it? Pour out a tiny amount and set light to it?

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    Welcome to Motor Vehicle Maintenance & Repair! Commented May 4, 2018 at 1:15

2 Answers 2


There are several ways you could identify the contents:

  • How does the fuel feel like? Is it a lubricant or a solvent? The lubricant would be diesel, the solvent would be gasoline.
  • How rapidly does the fuel evaporate? Gasoline readily evaporates, whereas diesel doesn't.
  • How easy is it to set it to flames? Gasoline will due to its evaporation ignite very easily, whereas diesel fuel needs to be atomized to small droplets by a spray can. Remember, it's not the liquid that is burning but the vapor. Be careful, though, as gasoline is extremely flammable. Only use a very small amount in a very well-ventilated area where burning the fuel is safe.
  • What is the density? Gasoline is 0.71-0.77 kg per liter, diesel is over 0.8 kg per liter. However, this is a bit cumbersome way to do it (you need to measure both volume and mass), but should work.
  • Both evaporation and flammability worked great - a teaspoon in a shaped piece of tinfoil was plenty. Thanks!
    – lunix
    Commented May 4, 2018 at 19:44

If you pour just a little (very little) bit out, gas will evaporate, diesel won't. If you rub some on a flat surface, you should see the gas evaporate really easily, but the diesel will just make it slick.

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