Please tell me your secret to such outstanding gas mileage.
Is yours a K1500 or K2500? Tire size? Vehicle weight? Gear ratio?

My sig describes my rig. I also have a fiberglass, cab-high canopy and the truck weighs a little over 6100 pounds with me in it. Before the Nelson tune, the best city/hiway mpg was around 14.5. Average was around 13.5.

In the three weeks since the new PCM, the best combined mpg has been 15.6. And I typically drive less than 65 mph.

I've been running straight 89 octane since the tune. But the first tank on the new PCM actually had a mix of 87 and 89 octane fuel. Driving conservatively, I saw 15.6 mpg. I was thrilled. I expected even better mileage once I was running straight 89.

But the two tanks of 89 octane since then have netted 14.7 and 13.4 mpg respectively. What gives?

Yeah, who can resist the sound and feel of a 6.0 that's no longer reined in by TM but I haven't gone crazy. With the tank that yielded the 13.4 mpg, I was actually behaving myself. Why is the mpg going down?

Hopefully, my average mpg will be better than what the stock tune and 87 octane was giving me. (assuming my foot lightens up) But this latest drop-off has me worried. I hope I didn't break the PCM...

In the meantime, please spread your wisdom/details regarding your truck's great gas mileage.

You're my hero!

 

dude you have a 2500HD
I have a 1500

You have an LQ4
I have an LQ9 (more compression = more efficiency)

you have a tank 4L80E
I have a little 4L60E

You have 4.10s
I have 3.73s


I have 265/70/17s, good air pressure. My tune is also for 91-92 octane.

My gas milage goes to **** if I run 87 or I run 89 and it gets hot out (or I tow)



the big thing is to NOT accelerate. Just keep it at one speed. thats the mathamatically best way to do it.
drag increase exponentially with velocity
so if you average 10mph and go 10mph the whole time - 10^2 =100
if you go 5mph first half and then 15mph the second half - the average of 5^2 and15^2 is 125. 25% more drarg!

Cruise control also hurts me for some reason?

 

See, I knew you were gonna say it was some type of heavy-*** truck I would say you are driving it RIGHT! That is some crazy mpg for you to get. Just keep it up. Do you have any mods on the truck?


All I can say here is that you can anticipate hills whereas the cruise can't


And for the record, I'm at stock height.

 

Yeah, weight isn't that big of a deal, but when you factor in 4x4 system and its losses on top if its weight and the weight of the ec, it can add up.

I have catback and pcmforless tuning (plus the Lq9)


Also, when you coast, try to really coast. As long as engine rpms are about 800 or 1k or something, after a few seconds of coasting, the engine shuts off fuel. So if you're coasting- just coast! dont coast for a second, hit the gas, coast etc. tapping the brakes might also do it.

No quick/hard acceleration, keep that converter locked (hence why I say dont accelerate- just stay at one speed). If you see a gradel coming, slowly start to give it some gas in peparation so you're not 3/4 throttle up the grade! Go from your cruising 70mph to 73 or so and then kinda just hold that throttle position up the hill- you might end up at say.... 67mph at the top, but thats better than unlocking the converter to stay at 70 from my experience.

Bryan does a hell of a job on his PCM's though. I've had 5 different engines tuned by him, all great work. He wont enable lean cruise because he says he wants a solid 30kish experience w/it on a truck before sending it out. I told him I'm first in line when he does

just little things i guess.

 

OK, OK, I know I have a 'tank'. No need to rub it in.
(it suits my outdoor lifestyle...)

But I did NOT know what version 6.0 truck you had. Thanks for clearing that up.

I understand what 10.0:1 compression, less weight and higher gears can do for gas mileage. Same goes for consistent and conservative driving habits. Even so, I am still impressed with 23 mpg from your truck. It takes discipline to feather the gas pedal.

You're right; Little things, taken together, can make a big difference.

I considered opting for a 91 octane tune but figured buying premium fuel would be a waste of money on a 9.4:1 engine. I'm not convinced it would've netted enough of a power increase to justify the expense. If I had your truck's engine though, I might've done it. (what was your LQ9's mpg before the improvements?)

Since I don't tow that much, I've been considering switching from 4.10's to 3.73 gears. That is, once I'm finished bumping up the torque a little more with a better flowing muffler.

GM gave the stock K2500HD 4.10 gears for a good reason.

 

I dont know what my MPG was before, but the 4.8 was 18, max, w/tune :wtf:
I did an Lq9/4L65E/Tune all at once

ohh, it was 22mpg


something else:
http://fullsizechevy.com/forums/show...&postcount=327

 

WHAT, I have a EXCB 5.3 and I am getting at best 13.5 MPG with a mix of about 1/2 city and 1/2 highway, If I could get to 18 I would be completly happy!
How do I do it!

 

mine was pure highway :p

 

my most recent pure highway was 15mpg.... see mileage test results thread