Maximizing LLY fuel mileage

[Uncle Wally]

It's been a while since I've posted on this. Figured it was time to do some updating.

I've had a couple hand calc'd tanks of fuel through the truck that were right around 20 mpg. Nothing consistant enough to say it's reliably doing that.

Couple of things I noticed:

Since the mandated Ultra Low Sulfer Diesel, I've noticed mileage drop about 2 mpg.

There weren't any changes with the truck until June when I finally got the Alcoa's with 235/85 16's on. I figured that would increase mileage a mpg or two. It did the exact opposite. I now run 200 rpm less at 55 mph, but mileage dropped. It either has to do with the rolling resistance of the A/T Revo's or the wind resistance due to the 2" wheel spacers between the duals. Not sure yet. I might try to remove the spacers, inflate tire pressures to keep sidewalls from rubbing and give it a go. That should answer that question.

Then in August I had some electrical issues that forced me to reinstall the stock tune. The problem hasn't been fixed yet because the dealer couldn't figure anything out. So the stock tune remains until further notice.

Now I have something leaking fuel somewhere. I can smell it, and it doesn't always start.

Bottom line.....

Fuel mileage the last month has been between 10 and 12, hand calc'd. 57K. New Blizzaks. No load. 10 minute warm up prior to driving. It doesn't get driven nearly as much with these rediculous fuel prices and the lack of decent mileage.

The two monthes prior 13-15.

I sure hope fuel prices correct themselves soon. At a C note to fill it, I'm getting frustrated.

Waldo

[bubbancolo]

Just bought my 2004 3/4HD Duramax longbox and drove from Colorado to California. Using the DIC I got high 18s driving between work and home the first few days prior to trip. Speeds didn't exceed 65 and had stop and go driving some of the way. Once we hit the interstate on our trip we only saw ~17 mpg, lots of hilly grades getting into Wyoming and high head winds. Once we started west bound at 75mph on cruise I got 18.7 mpg, I checked manually and DIC was within .4 mpg of actual. Now once I let the wife drive she set cruise at 80 mph and mpg dropped down to 17.8 mpg.
I filled in Reno and drove up and over Donner Pass and down into Chico speed limit was 65mph on freeway and ended up driving many back roads at 35 - 45 mph, on that tank I got 20.5 mpg. Truck is completely stock and has 26K miles on her. There were 3 adults and two children on board.

Running with my 8.5 foot truck camper (pop-up style) @1600lbs +gear=total of 1800lbs~ and a ATV trailer with two ATVs added another 2200lbs, running back roads and in the mountains taking on several passes and using tow haul mode and keeping my speed no higher than 65mph, my mileage runs about 13.8 mpg.
WOW I love that trans! Makes hills disappear and control in turns great. Oh stopping was much better with trans downshifting for me!

[larryh1]

I am running the Hypertech on my LBZ. I got it after my Chevy dealer told me to get one. I drive it easy for the best gas milage also. The very best I have gotten is 16.5. I am going to a larger exhaust mainly for towing reasons, (the speed shop says it will lower my turbo temp's) but I hope I get some gas mileage out of it also.

My Hypertech has three programs; performance, performance tow, and safe tow. I generally keep it in safe tow because of the trailer I tow, a 30' toy hauler, about 8,000 loaded. I did notice better pulling power right away, but the truck didn't need the extra power. I was hoping for better gas milage, but don't see it. I don't really expect a whole lot of gas mileage towing, but I would like better when I'm not towing.

Can anyone who is familiar with the Hypertech programer tell me if I would get better gas mileage in the performance mode. I haven't run it in that because I'm afraid it runs the motor too close to it limits. I bought the truck planning on keeping it for a very long time and don't want to damage it. I have tried the performance tow ( book says this is for towing items less than 6000 lbs), but didn't see a difference. The trans shifted at different points but the torque and power felt the same.

Any replys would be greatly appreciated.

Larry.