Prevost is a French-Canadian motorcoach manufacturer currently owned by Volvo. Headquartered in Sainte-Claire, Quebec, Prevost has earned a reputation for buses that are easy and comfortable to drive, with great handling and ergonomic driver cockpits.
My rule of thumb when I was shopping for a bus was a well maintained gas bus with under 100,000 miles or a well maintained diesel bus with under 200,000. In theory, a well maintained diesel engine can practically run forever. I drive city buses. They often have multiple million miles before they retire them.
Diesel powers over 90% of all school buses thanks to its combination of fuel safety, energy efficiency, reliability, durability, established fueling and maintenance network, range and operational flexibility, secondary markets and low acquisition and operating costs.