If you filled your tank with diesel on a freezing cold day, and then left it to heat up to a hot summers day, the (example) 15 gallons of fuel that you originally put in will expand to 15.3 gallons. So, worst case scenario is going to be avoided by using 0.3 of a gallon from a full tank to give enough space for expansion. That's about a 20 mile drive. But there's not many days where it's freezing and summer all at the same time.
Petrol is a different issue, as it has a far higher expansion coefficient.
Petrol is a different issue, as it has a far higher expansion coefficient.