Finally putting it on the road

It takes a little time to learn how to get good mileage with the big cam.

Initially I was getting between four and a half and sometimes 5.

This last IFTA quarter that I filed I'm at 6. That is with an fld120 with no fairings, tires similar but not exactly matched, no low-rolling-resistance tires, no wing on top of my flat top so the van is like a parachute in the wind, no skirts or fairings or any of that.

If I did all of that and switched over to the 13 speed I'm sure I'd be 6 1/2 to 7.

If I put my engine into an aero truck I probably would get 7 1/2 to 8, lol.

 

When I ran from Huntington to Gary, IN area grossing 80,000, I was getting 5.25 out of my Big Cam loaded both ways. But mine is not stock and does not struggle even with a 54,000 lb excavator on the lowboy….

 

My last Cummins was a BC1 400 in a K100. Once I got it fueled up a bit I got 4.2-4.7mpg out of it at 124,000lbs on 7 axles. I don’t know if that one @85COE has is set to whatever that CPL will take but it would probably like it if it’s not already. Those engines don’t have a full range governor on them though, and it’s pretty easy to over-fuel them. You're used to one, but someone used to electronic engines could discover .2-.5mpg just in getting used to fuelling a cruise-less mechanical. Could be another .2 in a hot-set, those engines responded well to that. I just hope he’s having fun driving the old thing. Not many people view the scenery from one of those anymore. The fuel numbers will come the better he gets to know it.

 

Lowpro 24.5 tires are the same as a full size 22.5 Tire, or very similar anyway.

I don't remember the exact gearing but I think your truck is geared really high. Having those tall tires on it doesn't help. I'm sure someone would know more exactly but the Low Pro 22.5 will probably raise your RPMs at least 500 as you Cruise.

The smaller tires will gear your truck down a little.

 

If that truck has fleet spec gearing that’s probably part of it. He’d have to be down a gear or going 85mph to run the engine where he’d need to for any kind of fuel mileage. They shouldn’t let accountants spec trucks, that’s how those fleet guys ended up with all those 3.5mpg 290’s too.

 

Oh, right, probably should have mentioned about the fuel mileage. Certainly not 2022 and beyond, compliant. However, what you lose in mileage, more than makes up for it in simplicity. Quite frankly, you are running that old gal a bit harder than you should, older trucks make great local or regional haulers, where fuel mileage isn't such a concern. Other than that, still sounds like good old PITA trucking,,,

 

I know how you feel missing the cruise Lol. Set it and ride.

Just got the Jake hooked up last weekend after converting it back to a mechanical. Still need a switch hooked up to the pedal but it makes the heavy loads easier using the Jake from Lo to 1st

 

Your tall 24.5 going to low pro 22.5 would be almost 4in difference like dino said that would be 400ish rpm higher

 

note the revs per mile in the chart.
moving from 11r 24.5 to 11r22.5 will slow you to 95% of your speed at a given engine rpm in each gear.
11r 22.5 and low pro (285/75r24.5) 24.5 have the same revs per mile meaning that that 95.4% jump can be done with your old 24.5 rims.
Moving to 295/75r225 tires from your 11r24.5 will drop your engine rpm by 92.5% at the same speed.
Any move to low pro tires will give you a very slight increase in fuel economy (1 to 2%) due to less flex and heat buildup.