I'll add some gasser info.
Not the first time I've typed this but can't find original to quote, I'm not going to debate gas vs diesel, to each his own.
My dads tow rig/ fishing truck:
97 K2500 suburban 454. 285's w/ 4:10s. Paid $4600 for it with roughly 50k miles from a dealer that sells a lot of govt fleet vehicles. Manual windows, power door locks, rubber floor.
Empty gets 13-14 mpg.
Towing 9k lbs on flat ground 9 mpg.
Towing 9k lbs in the hills 6-9 mpg.
Has no problem keeping up (65-75mph) with 05/06 cummins 6spd with similar load.
My 04 avalanche k2500. 8.1L. 285's with 4:10s. Paid $13k for it w/ 86k miles. Loaded w/ all options, even desired color.
14.5 mpg empty @ 75 mph
9 mpg empty in town.
1 mpg decrease towing 3k lbs 6 x 10 enclosed trailer.
Towing 7400 lbs, 9 mpg @ 70-75 mph, flat ground.
Towing 7400 lbs, 6-9 mpg @ 55-70 in the hills.
Towing 7400 lbs, 3 mpg @75 up hills like fancy gap/ black mountain, maintaining speed regardless of throttle/gear selection.
No problem keeping up with 05-06 stockins cummins 6 spd and my dads 454 above. Except when jeff drives the cummins like it's stolen.
Work truck #1, old tow rig.
01 k2500 suburban 6.0, 265's w/ 3.73. Loaded. Not sure initial cost. My mom bought with with 20k miles in 03. It now has 240k miles.
Empty gets 15 hwy and 12-13 city.
Towing 3k lbs enclosed gets 12mpg @ 70 mph.
Towing 3k lbs enclosed gets 9 mpg in town.
Towing 7400lbs gets 9 mpg @70 mph on flat ground. Will not run 75 mph consistently without downshifting and up shifting.
Towing 7400 lbs gets 6mpg in the rolling hills on the hwy @ 60-70 mph.
Towing 7400 lbs on the big hills gets 3 mpg. This is 2nd gear 45 mph @ roughy 3500-4500 Rpms in the sweet spot. This is all it will do. Multiple times dropped to first gear @ 4k Rpms, 17 mph, and turn the heat on high, a/c off, and windows down.
Will not keep up with anything above.
Work truck #2.
99 k2500 suburban 454, 3.73s, 245's.
Ex-secret service truck. Pulling 7400lbs will pass my dads 454 suburban pulling 9k lbs.
Gets identical fuel mileage as his 454 k2500 suburban.
This truck also gets identical fuel mileage as
@stinkbomb v10 f250 towing his truggy on trailer.
Verified it towing from Johnson city to evarts back to Johnson city. Although I believe his truggy on trailer to weigh less than my jeep on trailer @ 7400 lbs.
These are hand calculated numbers and known distances from towing between eastern nc to easter tn, and ky, and to western PA multiple times.
Daily I pull a 3k lbs enclosed for work.
Not only is the initial investment much less with the gassers, we save yearly with k2500 suburbans by using regular $29 car tags. No need for weighted tags with suburbans. As I understand the law, we are covered towing up to 10k lbs with them being titled as "passenger vehicles".
I wanted an 04ish 2500 suburban when I bought my avalanche in 2013. I found the avalanche and suburban with same color, miles, condition, engine, options etc.
The suburban was priced $6000 higher than the avalanche. This savings is offset by the 17k lbs weighted tag required for the avalanche that is not necessary with suburban.