I've done a lot of reading and testing myself on gas mileage and have come up with a list of how to obtain optimal gas mileage. Much of it centers around driving style. Not all of this necassarily applies to FWD vehicles.

Here's my list for maximum gas mileage:
- Use cruise whenever possible, or else keep as steady a speed as you can.
- Keep your speed down on the superslab, 65 seems to be a happy medium, or 60-65 if you can handle it.
- Keep tires properly inflated.
- Minimize a/c use. Roll down windows only in-town. If you have vent windows, USE THEM!
- Accelerate smoothly, steadily, but not too quickly; rule of thumb on a V8 is to try to keep your revs under 2000rpm on acceleration, if you have a tach, or under about 2200-2500 on a V6.
- In town, drive looking well ahead and coast up to stoplights, trying to keep your mass moving as much as possible when the light turns green. Saves on brakes too.
- Keep motor well tuned.
- Keep the air filter oil fresh by changing them regularly.
- Use the thinnest differential oil allowed in your differential.
- Keep o/d on at all times, unless towing.
- Lower (higher numerical) gears will often improve in-town mileage, and degrade highway mileage.
- Custom exhaust (for those of you gearheads like me that love hearing their engine pulsing away) can improve MPG slightly, but will take a LONG time to recoup the cost.
- Custom engine tuners like Superchips, etc. similarly will take a long time to recoup the investment on MPG, but can provide other benefits.

I'm sure there's a few more, but I can't think of them right now... but I can't stress enough that best, cheapest mod you can make for improving your MPG is ligtening your right foot!

 

I totally disagree about the cruise control, it'll use more gas (unless you live in the midwest plains)

I drove my dead grandfathers '98 Deville for 6 months & it had real time & average gas mileage gauge

I can get my average stay around the 32mpg range going down interstate 70 (to my ex GFs college)& if i used cruise, it'll average 24-26mpg

& you wanna know why???

it lets off going downhill (which it should) but it doesn't know that a hill is coming, so then its forsed to accelerate back up the hill, burning more gas, i got so good driving that damn thing stretching the mileage, a little accel down the hill & let off lightly going back up really helps stretch them MPG

it had a 19-20 gallon tank, took normally 17 gallons to fill up, & i've gotten over 325miles per tank several times, actully 325 was when i ran the **** out of it street racing it up in Hanover...it runs high 14's in the 1/4, i couldn't help but beat up on the ricers whilst in top luxury, hehehe

this was in a 4100lbs ( if i remember correctly) bigass caddy, with the windows always down, & a 4.6L Northstar V8

-greg

 

Rolling hills will murder gas mileage no matter if you use cruise or not. Physics states that what speed you gain going downhill is more than lost going back up thanks to drag and friction. It's a proven fact, cruise control saves gas.

Also, I'm not sure how much I'd trust the trip computers, especially just looking at the instantaneous readout. I always calculate by hand after I fill up. The only way to say for sure if what you say is true is to hand calculate at least a couple of tanks using cruise, and another couple of tanks without. All I know is that these tips worked for me in my last vehicle, a '92 Bronco with 302 - I went from 8mpg average to about 14 in a 4700lb vehicle with the aerodynamics of a parachuted brick.

 

We've just spent 3 days and 550 miles on nearly all highway. We spent the majority of that time with the cruise set on 75 on I40. My gas mileage for these 3 days has been 45 mpg. I am not kidding! We've had a family member in ICU 65 miles away, so we leave early in the morning, and come home in the evening to sleep, then repeat process. The hospital and the house where family is staying are each about 1/2 mile off the freeway. Our house is less than that off another highway. Granted, I am in central Arkansas, and there's not a lot of hills around to play with mileage. I was shocked when we finally got home for the final time and calculated the mileage.

 

Hey greaseangel that's good news! When I go to Wisconsin to buy Powerball tickets (if it goes above $200 million) I'll try doing 75 mph too.

I think what happens when you speed is that the engine goes into higher rpms where it produces more torque and horsepower per rpm, and then it goes into 4th gear (supposedly) for the higher speeds. Maybe that's why it gets better mpg above 65 mph!

I forgot about my aerodynamics, maybe when you go above 65 mph the air flow goes from laminar to turbulent thus less friction? I don't know but if this happens maybe it is better to go speeding for better mpg! We just have to watch out for the cops!

There might be a certain speed that's the sweet spot for best mpg on the highway, but I guess that might vary by the van year and engine size.

 

Every engine has its sweet spot, although every overdrive equipped vehicle I've ever driven had it occur at 45-55mph....but it's conceiveable that there may be one at 75 in these vehicles as well.

 

Hey guys , How about Tire Size, my 99 Caravan averages about 18mpg, I use a Fram air cleaner, ac delco plugs, I keep my tire preasure up, 4 wheel alingment up, and the least amount of weight at all times. This van has 13in tires. I wonder if I goto 14in tires if it would help? I recently put an oil charged K&N air cleaner in my 92 Chevy Siverado, 305 , 4X4, Z71, with running boards all of the way around, and a Hard Top on the Bed, with full bench back seat. I got about 4-5 more mpg out of the K&N air cleaner. Back to my 99 Caravan I am looking forward to the K&N air cleaner, a hotter pug, high performance coil, 14in wheels, synthetic oil, and I,m researching these new additives for the oil, tranny, and cooling system that is supposed to make them all run cooler. Any comments on these mods would be greatly appreciated.