RE: the sweet spot:

You don't like low-class jokes with THAT avatar????? Talk about mixed message.

 

Well you start by rolling over on your stomach and...Wait- WHAT?

Oh, the truck- OK, which sweet spot are you looking for? Fuel mileage? Torque? Horsepower?

For fuel mileage, you have to document and experiment for a few months then go over your notes. You should be able to figure what conditions and speed gives you the most efficient mileage.

For torque or horsepower, you will want to access the engine manufacturer's data and info for the exact engine in your tractor. I've never tried to do it, but I've bought new trucks that had the manufacturer's user's manual in it that listed those specs with graphs for each engine model.

Maybe you can search online for it?

Good luck!

 

Volvo has it marked on the RPM Tach on most of there trucks. Comes in handy

 

if you can get the volvo running !!!!

 

65mph on my Softail...... purrs like a (big) kitten, chews asphalt like a jack hammer!

 

as a sweet spot i consider place with lowest fuel consumption

here we had before diagrams with fuel consumption chart which shows on which rpm you get which fuel consumption rated in g/kwh

today only MAN offers such thing but manufactures still say: "it is best to run engine on 1200rpm" recently scania says that new engines can be in 1100rpm

 

1200 rpm & my 11.1 ser 60 is definitely lugging.

 

maybe in US here some trucks have less than 1000rpm at cruising speed

i remember one 1999 MAN my brother used to drive it had 900rpm at cruising speed so it cant be driven in last gear in most time he drove it in 14th gear ( 16total)

it had lowest possible tires in EU and according to my calculation 2.2 diff ratio 0.84 overdrive (1/2inch lower than 255/70r22.5) i dont know which revolution it had

 

Sometimes I think I have enough power to upshift on a hill & don't, & drop in at 1200. when I hit 1200 rpm's even if it's only for 3-5 seconds, later I can look at the stack & see the slobber from it.