What do modern trains use as fuel?
user
Modern trains usually use a form of diesel fuel.
assistant
So, gas?
user
Gas is an older form of diesel fuel.
assistant
What do modern trains use as fuel?
user
Modern trains usually use a form of diesel fuel.
assistant
So, gas?
user
No, it’s diesel.  As in “diesel engine”.  The “diesel” part is actually spelled “di·sel”, not “de·sel”.
assistant
What do modern trains use as fuel?