Keep tires inflated to correct pressures. This also extends tire life. Check tire slippage and add weight if necessary. Slippage can be estimated by measuring the difference in distance traveled per tire revolution when pulling a load and when unloaded. Check drive tires for excessive wear.
Worn tires can cause wheel slip from poor traction and increased fuel consumption.
Radial ply drive tires have more flex in the side wall of the tire which results in more traction when compared to same size bias-ply tires. Tractors that pull heavy loads are good candidates for radial ply tires. The increased costs of radial tires is usually more than offset by the increased traction, fuel savings and extended tire life. Dirty fuel injectors can cause inefficient combustion of fuel and some loss of power. Clean injectors if you see black smoke coming from the exhaust.