[HUMMERcustoms.com/TAZ]

Guys you are worrying Yourselves over allot of nothing. These rigs are not designed for fuel economy. I know the guy who programmed the Proflash and the guy who works for comp cams programming their FastFlash. Just max it out and have fun. You will not get any better milage with these tuners. The way to get better MPG is to use less fuel and these things increase full usage if You do not keep foot out of it. Get it so that you can tow better, run faster, or stock when You do not need the other. With the programs your are setting them for, performance you will not improve your MPG, there are exceptions. If anything it may go down due to the lead foot syndrome. If You want the best MPG go to factory settings and just add cold air intake, throttle body spacer, better spark plug wires anything You can find that will help the engine burn all the fuel better with a hotter spark. Increase the air volume to lean the fuel out and mix it better for better combustion at the same time without messing with timeing etc. Now going to the perf. could get better milage since your are leaning the engine out but, you have to keep Your foot out of it and after You feel the fun it will not save fuel.

I went full perf. and My milage stayed the same as stock. Except when I got to playing and having fun with the new power.

I have gone to Magnuson and when I finish with tuning even at 93 oct. I will be able to return to factory MPG if not better. These rigs are set from factory to run so rich it is not even funny. For an example My tuning on My SC right now shows air/fuel ratio is running -.9 with 12 lbs. of boost. The perfect number is -.08 to
-.09 I will come back to -1 and even though the numbers seem small to go from -.9 to -.1 it is huge fuel savings. it is so rich the tail pipe is turning black. We cannot tune anymore right now as We are doing the A/V for the next show and hoping to paint ghost flames and 3 coats of clear.

I had all My gauges setup and running while using the Proflash before SC and at full perf. on every item i was running full rich at WOT which is where You have to be concerned not to be lean. Guys nothing is written in stone and every engine is a little different but, the handhelds have to tune rich as they have a quaranty to worry about. but running rich also can cause problems with engine so be careful there also.

One thing You do gain by running full perf. and using 87 octane is more power. That is because 87 is more volatile than 93 which delivers more power because of the instability of 87 octane.
Do this at Your own risk but, this is my experience from working with hand held programmers since 1999. To run 87 with performance make sure you are getting cold air intake to lower fuel temp to prevent detonation.
I have a 1999 Silverado with 5.3 and it has been running the way i desribed with a Hypertech from first week I got it new off the lot with cold air, throttle body spacer, Granatelli MAF and changing spark plugs before the 100,000 miles and serviceing tranny twice a year. Cheap insurance. Have never had problems and does not use any oil to speak of between oil changes. I run a machine hard as I figure they are here for me to enjoy so I do not follow break in rules and run the dog out of them all the time. My H2 was picked up at the dealer on a Friday morning and left a 3 pm for Dallas at 80 MPH most of the time. I believe breaking them in as you are going to use them. I have seen to many pampered vehicles have lots of mechanical problems. Maybe just accident.

We are going to experiment with water/methonal inj., CO2 spray on the intercooler, and if needed but, more for looks a nice billet dry ice bucket at WOT. We are going to have the computer tuning software by HPTUNERS not hand held setup to run at all times when key is turned on so We can watch the air/fuel ratio real time and mess with slowly going down to 87 octane in place of 93. I absolutely do not recommend it if You are not going to add all the gauging needed to watch what is happening. My built in PC will boot every time I turn key on and will load HPTUNERS software tuning the first thing after OS is up and running so I can immediately go to scan and watch the A/F.
Well hope I helped some
TAZ