Let me start off by saying that my vehicle is very hungry for fuel. The necessity of hauling and towing a trailer for work relegates my vehicle choice to a HD 3/4 ton. My truck was a '98 GMC 2500 HD running on propane until it was in a fire a few months ago. The cost of driving that truck on propane was quite low. One time I calculated the economy for a highway trip and found that driving easy I could get 27 MPG equivalent. What I mean by 'equivalent' is in order. Propane costs less than 87 octane here by quite a bit. You lose mileage due to the lower energy content of the propane vs. gas, but the overall net is a lower cost. So using the cost ratio between the two fuels multiplied by the actual MPG (Imp.) I came up with 27. Pretty good for a full size 4x4 truck with the largest canopy available. Note, I'm Canadian so I use Imp. gallons, but for the sake of clarity I'll only refer to US gallons in the future.
Now fast forward to the present. A 2006 GMC 2500HD 4x4 sits in the drive. Technically the motor should be more efficient through design (plus the old truck had 325k). Right now I'm in the very early stages of finding out what basic things can help the mileage. Tire pressure at 50 and then 75 psi seems to have made almost no difference unless towing a trailer... except that the ride is harsher. I've purchased all synthetic fluids and will monitor the result. Next was to change the tires to something slightly taller and narrower. After that, perhaps a computer programmer or burning the chip. I've heard that the programmers mostly play with the transmission shift points (auto) to feel more powerful but generally don't change the MPG in the downward direction much. The same person told me that the a company they used burned a chip in three similar vehicles for fuel economy and results were between 3 and 8 mpg. When you are starting off between 13 and 15 MPG that is a HUGE change! If I got 2 from such a change I would be very happy. A serious loss in power is what I expect from an improvement in mileage this large, and I am fine with that. My old truck had a 5.7l vortec which had covered 325k. This one has a 6.0l with much lower mileage and a higher starting point for power and torque. I'm willing to bet that I could happily get by with 1/3 less power than it has 99% of the time because I don't use that power the way I drive. BTW, I don't have a scanguage but the driver message center gives me a fuel economy read-out... which may not be totally accurate, but it shows trends and changes. The very best average I've gotten while not hauling anything was about 15.8 MPG on a tank (confirmed by my calculations with a log). So I am open to ANY ideas people have to improve this truck so long as the truck can still work as a truck... otherwise I would by a Honda Civic.
Oh, I almost forgot to add that I'm looking into cargo covers right now. Tonneau covers and canopies to protect tools that I often carry from the elements. They either have to be easily removable or collapse so large items can be carried. What about having a retracting soft canopy like the Softopper for covering most loads with a partial tonneau cover most of the time to reduce tailgate drag?
Thanks to all on the forum. Already I've learned so much from reading many threads (I found the site because of the Aerocap discussion).
So that's my story...
Cheers,
Kirk