There are three (3) kinds of gasoline (fuel) at gas stations in Japan:
Premium grade, Regular grade, and Diesel.
Most cars use regular-grade gas, but some luxury cars require premium-grade gas.
Diesel gasoline is not used for passenger rental cars, only commercial vehicles or specified diesel cars.
Please remember that diesel can NOT be used for refilling the gasoline car (except for specified diesel cars).
If you do not know the correct gasoline type, be sure to check with the gas station staff before refueling.
Any problems, damage, or accidents with filling up with an incorrect fuel type is NOT covered by any insurance.
You must pay the compensation by yourself, NOT insurance.
Please be sure to check the appropriate kind of gasoline before filling.