Well, I usually get around 20 to 21 MPG. I just turned 20,000 miles yesterday and had to fill up today. I was stomping on it everywhere I went with this last tank and I got 18.9 MPG. And I mean I was stomping on it, I love speed. Anyways, I wanted to add my comments to this one.

 

One thing to remember, these cars are no lightweights. They all go over 4000 pounds. It takes fuel to accelerate that much mass or to maintain speed up hills. I live in Olympia, Wa (about 60 miles S of Seattle) and our hills are not as drastic as those up North (and the traffic is not as congested either) but I get 15 to 16 MPG average around town. If I head out of town on I-5 or 101 I'll see 24 to 27+ depending on traffic and terrain. The more I have to adjust the speed, the worse the mileage.

I've tried driving in "D" only being very conservative (that was a long week!) and then drove the car as I normally would in autostick mode all the time and really didn't see any difference in mileage. If anything, the mileage was a little worse using "D" only. I noticed I had to press the gas harder to get the car rolling in MDS mode and I used my brakes more for slowing for corners and school zones etc. with the car in D. I've been driving a big torque motor with a stick (stroked and bored 350) for 17 years now so maybe the autostick mode suits my driving style and expectations better. The car is more pleasant and responsive to drive in autostick mode.

I'm running a K&N CAI, Borla 112's cat back and Superchip set to 91 Octane, torque management minimized, and paddle shift - hold gear. The SC settings result in a 2 - 4 MPG increase over stock using the 92 Octane sold in my area. I did the Math and it's cheaper for me to run 92 rather than 87 despite the 20 cent per gallon difference. Shoooot, the increased performance and fun is worth the extra $3.80 per tankful.

I would still like to add a set of short tube headers, hi-flow cats and maybe pick up a Predator and play with those settings. So many toys and so little time .

Redbeard

 

Look at the type of gas you are using. Here in Houston in the summer months ALL of the stations have to sell a summer blend that costs $0.18/gal more, has less energy density, but complies with mandatory vapor laws. It is also referred to as oxygenated fuel. Also does your pump say "contains ethanol"? This will also lower your mileage. Are you using premium instead of regular? Premium has a lower energy density than regular gas.A tank full of unadultrated regular has the most energy, hence highest mileage, of any grade of gas. The tradeoff is that engines produce more power and do it more efficiently at combustion pressures higher than regular gas allows, so they have to add additives in order to make it not burn as easily, this is premium fuel, higher octane.
The higher the octane, the less the fuel wants to burn. The additives that make reular fuel into premium are mostly fillers. With the correct technology you could accomplish the same thing with water, changing regular into whatever grade of fuel you need. But it is extremely difficult to do properly, and can corrode internal components. I would not be suprised to see it in the future though, when premium gas is outlawed....
Now diesel, thats another story, it has a much higher enrgy density than gasoline. Who wants to have the first turbo-diese1 Charger? 350hp, 760 ft/lbs torque? Goodbye transmission.....

Yeaha, baby!