Nobody warned me about the MPGs on these square bodies!

[Grit dog]

I got an honest 11 mpg tonight with the Brodozer (deleted 2016 Cummins, slush box and 3.42s sitting on a 6” lift and 37s) pulling an approx 7klb vee nose 28’ snomachine trailer at 75-80mph. That’s almost 2mpg better than usual.
Then I realized why it was also so quiet and pleasant of a drive. I had a 20-30mph dead on tail wind the whole way. Was whisper quiet in the cab like I was only going 55-60 mph. So nice. That never happens. Usually it’s a fckin quartering head wind…all the inefficiency of a straight on head wind with the added bonus of steering wheel jerking gusts!

 

[Redfish]

I got an honest 11 mpg tonight with the Brodozer (deleted 2016 Cummins, slush box and 3.42s sitting on a 6” lift and 37s) pulling an approx 7klb vee nose 28’ snomachine trailer at 75-80mph. That’s almost 2mpg better than usual.
Then I realized why it was also so quiet and pleasant of a drive. I had a 20-30mph dead on tail wind the whole way. Was whisper quiet in the cab like I was only going 55-60 mph. So nice. That never happens. Usually it’s a fckin quartering head wind…all the inefficiency of a straight on head wind with the added bonus of steering wheel jerking gusts!

Careful my friend. If you keep Telling The Truth the full wrath of the Diesel Mafia will fall upon you.

Let's go over this again. "I got 18 mpg pulling my 10,000 pound trailer at 80 mph". You cannot let Truth and Facts interfere with a diesel mpg story. It's literally against the law.

 

[Grit dog]

Careful my friend. If you keep Telling The Truth the full wrath of the Diesel Mafia will fall upon you.

Let's go over this again. "I got 18 mpg pulling my 10,000 pound trailer at 80 mph". You cannot let Truth and Facts interfere with a diesel mpg story. It's literally against the law.

Ya fuel mileage people are probably the same clowns we’re talking about in the Craigslist thread….lol
But this truck is exceptionally bad with the lift, piss poor factory gearing and mostly the 37s.
Just like deleted gained me 4-5mpg. True ish with the pre DEF tier IV engines. Not true once they started using def and less fuel on regens.
Although may have done a personal best today. Clocked another 300mi of leisurely ripping country and mtn roads at 10-30 mph above the speed limit. But bobtail and not much over 60-65mph.
This truck has either been around town commuting or towing. Got an honest 15+ mpg. Not bad for an under geared over sized tire truck. Still drove it like a rental just not that fast.

 

[Turbo4whl]

3.08 gears, deleted cat, 3" exhaust from the collector back and rolling on 20's.

With a confirmed accurate speedo and odo, I was able to get 13.2 in a C20 with a 454. Nope, not one of those guys either. I couldn't beleive it myself. I was going easy on it trying to see if I could reach 10mpg and I got 13.2.

8 pages of fuel mileage. My question, are you all using an app to calculate miles traveled? Back in the day fuel number could be all wrong if the speedo was not re-geared. @Soundmound 's use of 20" tires is a good example how many mods these trucks can receive.

Skimming through these 8 pages @HotRodPC is the only reference I spotted confirming correct miles traveled.

 

[Grit dog]

8 pages of fuel mileage. My question, are you all using an app to calculate miles traveled? Back in the day fuel number could be all wrong if the speedo was not re-geared. @Soundmound 's use of 20" tires is a good example how many mods these trucks can receive.

Skimming through these 8 pages @HotRodPC is the only reference I spotted confirming correct miles traveled.

The size of the rims is irrelevant

 

[Terlingueno]

8 pages of fuel mileage. My question, are you all using an app to calculate miles traveled? Back in the day fuel number could be all wrong if the speedo was not re-geared. @Soundmound 's use of 20" tires is a good example how many mods these trucks can receive.

Skimming through these 8 pages @HotRodPC is the only reference I spotted confirming correct miles traveled.

The app I use is small spiral notebook that fits in the glove box, write mileage from odometer and gallons in off the pump with a pen or pencil, then proceed to use arithmetic to calculate mpg.

 

[Turbo4whl]

The size of the rims is irrelevant

You totally missed my reference. Many stated rear gear swaps. I'm sure many are not running stock tire diameter either. What is the diameter of a stock G78 tire on a 15" rim? You would almost have to run those 20" rims with no rubber to match the stock tire diameter.

 

[Turbo4whl]

The app I use is small spiral notebook that fits in the glove box, write mileage from odometer and gallons in off the pump with a pen or pencil, then proceed to use arithmetic to calculate mpg.

That's what I did too. I did put the correct speedo gear in the trans to match my 2.56 to 3.42 swap and tires.

 

[Terlingueno]

That's what I did too. I did put the correct speedo gear in the trans to match my 2.56 to 3.42 swap and tires.

My truck is bone stock, SM465, 4.10's, LT 235/85R-16s as it rolled off the line in Flint in '85. Except for a CUCV grille guard and the stereo...

 

[DoubleDingo]

8 pages of fuel mileage. My question, are you all using an app to calculate miles traveled? Back in the day fuel number could be all wrong if the speedo was not re-geared. @Soundmound 's use of 20" tires is a good example how many mods these trucks can receive.

Skimming through these 8 pages @HotRodPC is the only reference I spotted confirming correct miles traveled.

Negative ghost rider, post #2 stated accurate mileage, just wasn't broken down. It's in some thread I shared it in 12 or so years ago.

 

[DoubleDingo]

8 pages of fuel mileage. My question, are you all using an app to calculate miles traveled? Back in the day fuel number could be all wrong if the speedo was not re-geared. @Soundmound 's use of 20" tires is a good example how many mods these trucks can receive.

Skimming through these 8 pages @HotRodPC is the only reference I spotted confirming correct miles traveled.

This isn't the actual thread I'm thinking of, but this is similar info
Post in thread 'Carb'ed vortec looking for info and opinions' https://www.gmsquarebody.com/threads/carbed-vortec-looking-for-info-and-opinions.35037/post-713381

 

[Soundmound]

8 pages of fuel mileage. My question, are you all using an app to calculate miles traveled? Back in the day fuel number could be all wrong if the speedo was not re-geared. @Soundmound 's use of 20" tires is a good example how many mods these trucks can receive.

Skimming through these 8 pages @HotRodPC is the only reference I spotted confirming correct miles traveled.

So I used google maps GPS speed indicator and mileage coupled with my gallons used and odometer mileage. I can confirm my truck with 255/45/20's was turning exactly 70mph on the speedo when running 70 on Google maps. I clocked 13.5 mpg mixed driving, mostly highway. I'm good with that for its first real outing since I've owned it.

 

[DoubleDingo]

@Turbo4whl
This here is the thread I was thinking about. Much easier to search on a computer than it is on a phone...
8 miles per gallon

 

[Grit dog]

You totally missed my reference. Many stated rear gear swaps. I'm sure many are not running stock tire diameter either. What is the diameter of a stock G78 tire on a 15" rim? You would almost have to run those 20" rims with no rubber to match the stock tire diameter.

True story but these tires 245/45s and 275/40s are only an inch taller than a dinky little G78 15.

You must be registered for see images attach

My point was big rims don’t necessarily mean taller tires.

 

[legopnuematic]

I love the 4.10 too, but I figured different gears was less wallet invasive than a modern transmission

With a more or less stock driveline I’m not sure you’d see much for gains (strictly mpg, not cost of regearing, etc). 3.42 to 4.10 (same tire size) you’d be about 550 rpm difference.

There are tons of factors, both vehicle and environmental that contribute to fuel economy, far beyond engine rpm at cruise. Lower rpm doesn’t necessarily mean better mpg.