How do I convert gallons to liters for fuel?
The definition of the term gallon differs from region to region.
If you are in the US, a gallon (i.e., US liquid gallon) is $3.785\ 41$ liters.
If you are in the UK, a gallon is $4.546\ 09$ liters.
$$ \therefore \text{Volume}_{\text{gal (liquid) (us)}} \lt \text{Volume}_{\text{gal (uk)}} $$