Yes, diesels typically have longer range.
Years ago, I owned a 4x4 Suburban with the 6.2-liter V8 Detroit Diesel engine. The Sub went across the scales at 7,250 pounds, and it was the most gutless vehicle I've ever owned.
But even with 4.11 gears and lockers in both ends, 6" lift, 35x12.50R15" mud tires on custom steel wheels (including two full-sized spares in the back), 9,000-pound Warn winch with front and rear mounts, heavy fabricated steel bumpers, tool box, spare parts, spare fluids, shovel, axe, recovery equipment, etc., it got 20+ mpg on the highway- it's stock 40-gallon fuel tank gave it an honest 800-mile range.
We filled up in Vancouver Washington, and drove it all the way to Laguna Seca in Monterey California without refueling, towing a motorcycle trailer, with two motorcycles, all of our riding gear, all of our pit equipment, and all of our camping gear inside.