Weight vs frontal area
Recently I rented a 24 ft. 3500 lb. dry weight RV, to see what it would be like to tow. I figured the loaded weight to be close to 5000 lbs. My truck handled the weight okay but the 200 horse V 6...
Forum Discussion
boogie_4wheel wrote:
The weight of the trailer has the largest impact of getting moving form a stop (or coming to a stop).
The frontal area or drag of the trailer has more of an impact while you are traveling at speed.
I notice a big difference between pulling my toyhauler, and pulling a flatbed trailer with a tractor loaded on it. Getting rolling feels the same, but maintaining speed is easier; the truck doesn't work as hard.
x2 on weight vs. frontal area. From physics, once you are moving at a constant speed on level ground weight has very minimal effect on your mpg. Only to the extent that it effects frictional losses in tires, bearings etc. to a minor degree.
Frontal area affects wind resistance which is a square law function and has a constant effect on drag.
For comparison, I have a 7x14 ft cargo trailer about 5,000lbs full and a 35' outback 295RE, 9,000lbs full and a much larger frontal area. I tow both across the cascades to eastern oregon. The mileage difference between the two is 1.0-1.5 mpg better for the cargo trailer wth smaller frontal area (11ish vs. 12.5 ish). And that's going over some low elevation passes. Going up and down the columbia gorge where is it reasonably flat, the difference is under 1mpg.
In both cases I drop 8-10 mpg or so compared to unloaded the same speed. Wind resistance and frontal area kills mpg.
