A good tune up with quality parts, regularly.
Properly inflated tires.
Good driving habits, coasting, using cruise control, not maintaining speed up a hill.
Removal all non essential weight from the vehicle
Use of a quality fuel additive every few months to keep injectors clean....

There may be a few items out there that do improve mpg, but what you will spend for them you could use that to buy gas and be better off,
essentially the payoff could take years..

 

Did you check out Blackbear?

But like in2pro said, the payback may be years unless you drive a ton of miles annually.

 

At 12,000 miles a year the difference between 16mpg & 17 mpg at $4/gal. is only $180/year (not even enough to buy an extra gallon per week), and I'm willing to bet that most performance upgrades that benefit mileage will decrease in their benefit over time like your motor, not to mention that you're trying to make an engine do things it wasn't designed for which will most likely take life from it. You're probably better off just following in2pro's advice, spend your money on maint. which also equals longevity... but to add to his list...

-performance exhaust
-NON-ethanol gasoline IF you can find it, anymore you pretty much have to be in a rural area to get it, my '99 ran much better on it though, I hate this 10% ethanol junk.
-use quality tires and keep them at max recommended pressure, not the squishy psi the car manufacturers recommend, that's just for ride quality snobs, if you buy good shocks you won't know the difference.
-keep the exterior clean
-the best fuel additives I've used are Lucas & the stuff from Amway (not sure if they still have it). I actually tested it through several tanks to about 1mpg better in my '99 with it, but that was when I was using non-ethanol gas too, not sure if it has the same effect with the ethanol gas most of us have now.

 

Agree with you. I like getting into this. The Liberal mindset is to drive up costs of fossil fuel, take away drilling, so we can all putt putt around in crappy electric cars which no one wants. Oil company = EVIL. Environmentalist group= GOOD.

Lets go drill now!! North Dakota and Montana now have more oil than Saudi Arabia.
and in Alaska, the animals huddle around the pipes to keep warm. More drilling, or the hint we can do more, the statement alone will begin to drop the gas prices.

 

I agree with you on the fuel additive products from Amway and Lucas. I used to regularly get the AMWAY stuff...but they had quit making it. I heard Harley Davidson had the same stuff. I got 2mpg more in my 97 Concorde but this was 4-5 years ago. It was the best stuff. 2nd best is that Lucas gasoline additive...Almost as good for gas mileage enhancement.

 

I agree to this helps, its one of those long term payoffs but every little bit of drag counts... adding a bunch of wind/bug deflectors can be counter productive for fuel....somewhere in this forum the drag coefficient is listed for the gmt900 and its pretty decent, the front end for the Hybrid Tahoe is also something to consider as it also helps lower drag and help improve mpg....

 

I put around double average mileage about 24k give or take, I looked on blackbear but I cant seem to find what your'e talking about can you send me or post a direct link?

 

Here's one: Black Bear Performance :: Custom Tuning Solutions for 96 and newer GM Vehicles

Another: Black Bear Performance :: Custom Tuning Solutions for 96 and newer GM Vehicles

And FAQ: Black Bear Performance :: Custom Tuning Solutions for 96 and newer GM Vehicles

 

The 2007 numbers are: LTZ = .36, Z71 = .38, Hybrid = .34, Corvette = .29. So these 3 ton bricks aren't too bad.

 

Looks like there is no option for a '97, I had to get a new computer for my '99 and if I remember right there were some computers that were used for '98 and '99 and some that were used for '99 and '00, so the '97 must be different, I would just contact them to be sure though.