The weight of 35 inch tires coupled with the wind drag of the truck that high up kills it everywhere.

Alot of why the 2015 is doing better is the truck aerodynamically is alot better than previous years. Mine is 4wd and the air dam is no more than 6 inches off the ground... Kind of low if ya wanted to go offroading but I didn't buy it for that

 

2015 2500HD 4x4 SLT, 5" lift on 35's. Dash tells me 10-11, whether its stop and go, backroads, or interstate. Best on the dash shows 14.5 and that was staying under 68mph. Those numbers should be a little higher, as the speedometer isn't corrected and I'm 5mph off everywhere above 55mph.

I get the same milage according to the dash from 70mph to 85mph on the interstate. Due to tire size and speedo being off, I can not accurately hand calculate it. 17,500 miles on the truck already, might have seen 1mpg difference once I had 7-8k miles on it.

 

To hand calculate the mileage, I always picked a set speed, (30 on my speedo was really 35 mph), so I then set that up into a ratio. I would then divide my tripometer by the 30, and multiply by 35. After having my speedo reset for my 35's (Really 33"), I hand calculate it now and it's very siilar with the initial calculations. Hope this helps!

 

Flex a lite makes a electric fan set up for the silverado.

 

What I'm thankful for this thanksgiving... This thread lol thanks for helping me decide on a Christmas present for my boyfriend. Looks like he's getting an intake. (As well as new shift **** and new tailgate latch lmao)

 

Since this thread is already opened back up ill post my 2500hd..lol. Supercharged 6.0, 513 gears,37 inch tires with a 4l80e. The best it sees daily around town is 12 mpg, on a big trip i averaged about 15. Towing my trailer it stays 8-10 depends on how many big hills and thats with 8k.

Stock mpg with a cold air kit, exhaust and a tune the best it ever got was 14 around town.

 

easiest & best bang for your buck would be intake or air box mod, a tune, & long tubes with a straight-through muffler. do the speed limit, and if you have bigger tires, regear.

 

Biggest gain in mpg i ever saw with my truck was when i added the tonneau cover, sadly enough actually made about a 3.5-4 mpg difference.... Saw sonewhere a tonneau or cap is worth about 25% didnt believe it til i put one back on the truck!!!