Gas Mileage And Rpm

[firepoggy]

Ok I am completely new to the 2500HD world. I have owned many a 1500 but decided to upgrade to allow for a larger camper. Gas mileage stinks rotten with the new truck. I am wanting to know what RPM your HD runs at approx 70mph? I am right at 2500 and sucking fuel like there is no tomorrow. The truck is an 04 with the 6.0 and 4.10 rear. As far as I know the truck is stock, bought it a week ago.

[hcpyro13]

'06 2500HD w/ 4.10's

Motor is spinning 2500 rpms @ 72 mph... I've found I can get the mpg's over 15 it I keep it around 60-65 It is making me HATE the interstate I frequent. It's time for me to get some taller tires so I can get those rpms down a bit at highway speeds.

[ZsTB]

'05 2500HD 4x4 6.0, 4.10's, 285/75-16 BFG ATKO's, K&N FIPK, Magnaflow dual 3" in 3" out, Diablo Predator tuned.

 

60mph-1960rpm

70mph-2305rpm

80mph-2625rpm

85mph-2825rpm

 

My truck is run 90% highway, speedlimit is 75mph, I generally run 80-85mph. To get the best mpg your gonna have to keep it under/around 60mph/2000rpm's, and forget it when towing. Running 80-85mph I'm averaging 250 miles to the tank. Which I dont think is to bad since my '04 Trailblazer 4x4 4.2 averages only 30 miles more per tank.

 

Chris

[Shaners]

You will notice a significant drop in MPG's between 65 and 70 MPH. My old HD was an '01 w/6.0L and the best I ever got was 16.5 MPG (100% highway) with no air on and no cruise control. I had to run between 65-68 MPH to get these numbers.

[Cheekster96]

I have an '06 2500HD with the 8100 and six speed Ally.

 

At 70mph, the tach indicates an even 2000 rpm. This is with the 4.10 gears. I think the sixth gear ratio is .68. Not sure.

 

Later

 

Lee

[hcpyro13]

Anybody out there got some numbers for some 255/85/R16 tires? My choice is basically down to them or the 285's as my next tire in an attempt to bring down my rpms a bit on highway. Appreciate any feedback you guys out there can offer. Thanks.

[ZsTB]

The 255/85-16 and the 285/75-16 are pretty much the same over all in height (255's are a tad bit taller 33.1" vs 32.8" dependent on manufacturer), so you will looking at roughly the same revs as what I posted above for my 285's. You would also get a much better tire selection with the 285's as well.

 

Chris

[firepoggy]

Thanks for the posts!

 

Will dual exhaust help out at all? It has been several years and two trucks ago since I ran tips to the back bumper.

[Shaners]

The skinnier tire will have lower rolling resistance and better MPG's.

 

Unless you reflash your PCM, your truck will still think it has 245's on it. So, you will be traveling much faster at highway speeds than what is indicated. You will also be traveling more miles than what is recorded on your odometer.

 

BTW, my MPG's in my Dmax dropped by 5% when I went from the stock 245's to a more agressive 265/75/16. That said, a larger tire doesn't always mean you'll get better fuel milage. A larger tire requires more energy to start rolling from a dead stop, so most likely your milage in town will suffer. Also a larger tire has more rotational mass, so it requires extra energy to keep it spinning. In my case since I only went +1 in tire size over stock, I attribute most of my milage loss to a larger more agressive footprint with more resistance to the road... On my '01 6.0L I was +1 also, but I put a less agressive tire (Michelin LTX M/S) on the truck, so my milage stayed almost equal to stock.

[davzog]

I got a 2007 6.0L.....had it 2 months. Originally I was getting 12-12.5 back and forth to work, which was exactly what my previous Ford V10 got...

 

Now that it has 2500 miles on it, the miles it pretty stable at 14.2-14.4.....60/40 hiway/city.......I added a Flowmaster and an Airaid Jr....absolutely no effect on mileage but it sounds very nice!!

 

I used to have a Dodge diesel...never got over 18, BUT the maintenance was a killer (3 gallon oil changes, etc.)

 

You just can't drive a big truck and think it will be good on gas...won't happen...my fuel bill last month was over $600!!!....dammit!!!!

[2017HD]

I have a stock 07 nbs 4.10 rear gears and stock wheels and tires, 6sp tranny. At 60MPH I am just under 2000RPM and get a bit over 14 MPG when on cruise. I have not been able to take a real road trip at 65 - but the RPM is just over 2000. I find I get better MPG with a light throttle and keeping the Tach below 2500 RPM. My average MPG is in the high 12 range with mostly city driving.

[dizzy]

I have a 2005HD, 6.0L automatic. Changing tires won't help you any, that truck sucks the gas going uphill, downhill or sideways. Around town I'm lucky to get 10-11MPG, freeway driving, lucky to get 14MPG.

 

I also thought installing taller tires would help with MPG, that was a $735 mistake. I installed 33" BFG Mud Terrians, while it rode much better with those tires it didn't help the gas milage any, in fact it got worse and had less power. Just driving down the interstate going over an overpass would cause the cruise control to drop down.

 

Think I weighted the tires by themselves once, the stock tire came in about 33-35lbs., the 33" tires slightly over 50lbs. each.

 

I think there is a reason GM stuck those 30.5" tires on that truck, it is made to pull a trailer at 55MPH and that is it. If you want better gas mileage you are better off getting a 1/2 ton with taller gears and 265 tires and taller overdrive and putting on some AirLift airbags if you need the extra hauling capacity. Then you may get 18MPG on the interstate. I used to get 18MPG all the time highway wth my 2000 Silverado with the 5.3L, all it had was a stock replacement K&N filter.

 

So far on my 2500HD with 4.10 gears I've wasted money on:

 

Installing 33" tall tires (great for leg shots going down the road)

Installing Fram's FramBoost cold air intake (K&N's better)

Installing HypertechIII programming (doesn't help MPG any, if anything it is worse).

 

With that $1,400 I've wasted chasing better MPG, at $3.50 per gal for what I pay for regular gas I could have bought 400 gallons of gas which would have taken me 4,800 miles further down the road. I have 285's installed on mine, I would suggest not going taller than 265's, that is the same the 1/2 ton's come with.

 

[ZZ327]

youll probably have to get a gear change for better mpg 4.10s are gonna suck that bad boy down

[HDdave]

Thanks for the posts!

 

Will dual exhaust help out at all? It has been several years and two trucks ago since I ran tips to the back bumper.

 

I've got duals on my 01 6.0/ 4:10's with 285 goodriches. I run around 2600- 2700 at 70mph. It almost sounds like your truck is weird like mine and will run in 4th gear on the highway. I can run in overdrive at around 55 mph, but it will shift down when I'm at 70 and stay there. I just can't figure out what the problem is.. On the rare occaision that it will hit o/d for a few minutes on the highway I can run 2200- 2300 at 70 mph....

 

Forgot to mention that I have a true dual system with a K&N CAI, next mod is a tuner to mess with the shift points possibly, and get a little more power. The Duals helped my milage out by maybe 1 mpg or so, but they really sound nice and give a little extra grunt.

[wellinghurst]

03 2500HD 6.0 4.10 285 All-Terrains:

 

not sure why your tranny won't stay in OD-mine runs in OD all day long up to 100mph if I push it for fun. I can pull my boat uphill and unless its a very steep grade, it stays in OD. RPM just under 2000 at 60 mph. I drive slow with the occasional opening up-average 14 mpg-always at least 440 miles per tank.