The automotive world is extremely competitive and sales are driven by numbers. Two extra cup holders, ten more horsepower, or one more mile per gallon than the competitors translates into more sales, so you know if they could have squeezed out one more mile per gallon with simple modifications that maintained the legal emissions requirements, they would have done it. It takes a certain amount of BTUs of energy to move a given amount of weight, factoring in wind resistance and friction. You aren't going to improve on what the engineers came up with without spending a lot of money on technology that won't provide the financial payback. The biggest thing you can do with a truck to increase fuel mileage is to cut your highway driving speed by 5 miles per hour. This is even more effective with diesel engines.

Answered by caradiodoc (expert)
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