"Regular" is gasoline with an octane number of about 90.
High octane
"High octane" is gasoline with an octane number of 98 to 100.
Diesel
"Diesel" is fuel that is used exclusively in diesel-powered vehicles.
There are three types of fuel: regular, high octane, and diesel (light oil). When renting a vehicle, confirm the type of fuel that is used for that vehicle. If you fill it with the wrong fuel, you may damage the vehicle. Repairs will then have to be made by the rental company. The cost of such repairs will be borne by you, the customer.