Buying 2015 isx 2350 234k miles high hours

[Fast Hedgehog]

(10-05-2021 )FnG92 Wrote:  Is there a mathematical way to explain driving 63 instead of 65 or 68 (if legal) in regards to fuel savings? Let's say 1 more mile per gal and multiply by let's say 2k miles a week or something minus the same mileage but at 68 to see the cost of the extra mph in a theoretical breakdown of costs.

Simply put, there is no simple formula that calculates that because road environments are all unique. Charging 68 up and down a mountain will have vastly different dominating factors in efficiency calculations than driving on a flat road. Local driver (slower average speed) vs long haul (higher average speed). There are tons and tons of variables that could change dependent on tons and tons of situational variables. Driving on a new road vs bumpy road will change that calculation, road temperature, ambient air temp, what tires are used, what wheel lubrication is used, wind direction.... the list goes on and on.

The best way to do this is not to model an equation to calculate efficiency, but to model an equation based on your efficiency history. Keep a fuel notebook where you note mpg, type of driving, weight, idle time, ect and you will be able to find a trend for your situation.

Simple post on the aerodynamic forces: https://physics.stackexchange.com/questi...ent-speeds
Post with more derivations of equations: https://physics.stackexchange.com/questi...resistance

And that's just explaining power output needed from the truck. Now you'd have to do a ton more calculations on the efficiency of the process of getting the BTUs contained in Diesel converted to the torque at wheels via the engine, drive train, other parasitic loads.