Hunter of Trolls
Join Date: Nov 2012
Location: east coast
Thanked 175 Times in 136 Posts
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Wind resistance is exponential, so the truck is working harder maintaining 80mph than it is at 60mph (relatively speaking).. so... If it took 6 units of load to hold 60mph, it would NOT take 8 units at 80mph, but more like 10..
I've found that my truck, w/o hauling or towing, gets its best economy right around 65mph.. if you have a tuner you can monitor egt's... Setting speed based on that is a dang good way to drive economically.. keep them under 550*, let the engine dictate speed and not a sign, and you can get 18~20mpgs all day long, unloaded.. load her up with cargo or a trailer, though, and you're going to cut into that pretty good, but should still stay in the double digits..
While towing a load, ease into highway speeds.. use your foot to maintain speed (no cruise control) hold it steady over a decent stretch of road while monitoring your egt's... Aim for that temp for the rest of the trip.. you'll be slower than traffic often, but sometimes you won't be.. again, this is allowing the truck/load dictate speed and not some sign..
I'd love to find a cruise control device that sets speed at engine rpm or pyrometer.. it would pay for Itself pretty quickly I'd guess..