Is there any argument that engine components may fail sooner rather than later if the engine isn't operated in the published sweet spot?

Unless the RPMS are really low I doubt it. Electronic engines are pretty good. I think if you're light 100 rpms below the "sweet spot" is fine.

Next thing I'm expecting to see on here is someone saying that they cruise all day @900 RPM.:roll:

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No... it's pretty simple math... 57 mph on my GPS. The equation is
Tires=514 rpm (rotations per mile) x 2.64 (rear gears) = 1356.96 x 1.00 (tranny final ratio) = 1356.96 rpm @ 60 mph. 57 mph is 95% of 60 mph. 1356.96 x .95 = 1289.112 rpm.

My tach actually shows about 1375..

It depends...Some times, actually quite often, i have to "accelerate" a hundred times a day.....

Wow! It makes no difference to you, if that money go out of staks, or into your bank account?

With my Truck I tried it, and it did not matter what speed I went, I got the same bad fuel milage, 5.56. 55mph or 75mph. So I said why be a road hazard and go with the flow.

I simply found the very first post interesting b/c the poster did'nt take into account the other variables that others have already mentioned. Not every truck has a 13 speed or higher trans, everyones rears are different, and loads carried varies from 1 truck to the next. I know with my truck, a mid-roof volvo, w/ a straight 10 eaton, volvo d-13, 3.73 rears, and 48,880 load, my truck gets about 5.5 on level ground loaded. I never carry less that 47,000, and dead head back to the terminal when finished. My truck is goverened at 65. I average 5.8 over the length of any given run. On the other hand, another truck in the fleet with all the same specs, but having the ISX 600 gets better fuel economy than I do, and the empty combination weighs 1000lbs more than mine? I'm no math wizard, but I say to each his own, and for the record, with my setup, 65mph is at about 1550 rpms and still within the sweet spot zone. slower does improve fuel economy, but there is a point where one has to put good sense to use over fuel economy. If you get in an accident trying to save fuel going slow, than all the money you saved will just go to help pay your lawyers fees.

Same here. I get 4.5 whether I do 55, 65 or 75. So, guess which one I'm gonna go with (hint: it's not 55 or 65).

It has the most effect? How much more effect does it have than weights upwards of one-hundred thousand pounds? How much more effect does it have than 550hp+ fuel guzzlers? How much more effect does it have than hefty crosswinds or headwinds? I could keep going with the questions, but I'll stop there and agree that speed has 'some' effect, but not 'most' effect.