Either vehicle with that many miles will experience constant maintenance and you can expect some expensive repairs. The diesel will be more reliable than the gas at that mileage, the gas will probably need a major overhaul or replacement very soon. The routine maintenance performed by the previous owner will determine if either truck is worth purchasing with that many miles. If synthetic lubricants were used, it's a definite plus. How often the oil changes were made, standard transmission or auto, there are many variables. The ownership of the truck will involve other costs not directly attributable to the motor; brakes, transmission, rear axle, front end, four wheel drive etc. They are all subject to wear and their repairs can be a significant cost. Diesels usually sell for more than the gas because of their higher initial cost, better fuel economy under load, and long term durability. They are built more robustly than the gas engines, run at a slower rpm and their fuel is a lubricant as opposed to gasoline which is a solvent. This results in minimal cylinder/piston ring wear, much less than a gas engine. People who own diesels are usually very opinioned in their ownership and would not go back to a gas. Many gas owners can't wait to own a diesel. It's all about how you want to go down the road BOL Gard | 
Gas Engines Versus Diesel Engines?
