65mph vs 70mph

It's about rules of diminishing returns and practicality. It's about reasonable compromise. For some, it's 55, others settle on 62, most settle on 65, others don't give a crap [until the next fuel spike where rates don't keep up in a timely manner]

 

I drive a daycab governed somewhere between 75-80 and I've noticed I stop and get something to drink, stretch, and check the tires in no real rush..... then when I get back on the big road the slow megas I passed way earlier are just passing me or I pass them again in a mile or two

 

You mean like if I have 3 apples and you have 2 apples, how many pancakes fit on the roof?

 

It's a wash.

Mileage difference is 50 or so at the end of day.

One will gross you 365 and the other about 320. 35 to 50 miles difference between the two in speed. And about a dollar difference in gross miles paid between 49 and 47

I'll take the 70 truck in a heart beat.

 

Speed of truck doesn't change your appointment times. The paychecks are the same.
I know this from experience.

 

I would still take the 70 truck.
Yes the appointment time is still the same. But you are behind the wheel a shorter time. Laws of probability would be less chance of stuff happening.
I don't believe you can determine the time savings as a simple 50 miles. Too many variables. At 65 you come up on 5 or 6 truck line of 62-64 mph trucks. Not as easy to swing out on a moderate to busy interstate for example. There can be times when traffic, construction and such makes them almost equal. I just don't think it's easy to figure .

 

What if the 65 truck has 600 hp and the 70 truck has 400 hp?

 

As an owner Op I will take fuel savings any day. My truck will do 85 tops, but I keep at the posted speed.
If I keep her at the posted interstate speed of 75 vs 68 i lose about 300.00 per week running 2700 +/- miles; about a 14,400.00 year gain of loss how I drive. So I run around the 65-70 mark, have the hp and speed if needed to get around slow right lane traffic, but in the end running at the top of posted speed gets ME no closer to weekend home time then if I drive 65.

Oh wait to many variables, no my runs are the same 450 miles up loaded 450 back loaded at max 80K.

If I ran flat out and speeded all the time like the mega do through all the small towns from I 80 to I 70 north south I would only pick up a 1/4 of a load which makes no sense cause I would have to reset someplace other then home.

 

It's pretty common for faster drivers to assume they can stop more often or for longer periods and make up the lost time. When I was doing Nashville to L.A. in a 65 mph truck I was passed by the same fancy trucks several times per day and we would usually wind up at the same truck stop in Barstow within minutes of each other 2 days later.

 

Laws of physics also apply to the gearing and powerband of the engine, heck even the road surface plays a factor. Fact is the optimum mpg speed of a truck is going to change every day and its all going to be based on what the truck was specced to do.