Thanks everyone for replying to the post. All the info you all gave is helpful to me to get an understanding on how to get better mileage.

I'm sorry if I offended you in any way but I just really needed to know if there are any other possible way to help with the gas going up.

 

Have the laws of physics been flipped around recently?

Modern, computer-controlled cars utilize injector shut-off under coasting conditions. This means that your car is using essentially zero fuel when in gear and off the throttle. If you take the car out of gear when decelerating, the engine drops to idle and must use fuel to maintain it.

Using more fuel on decel than WOT? Now that is really a new one.

 

It's totally possible. Like speedjunky said, you can run the AFR a little bit lean in the cruising RPMs with timing adjusted a bit and this will help greatly. If you REALLY wanted to save money at the pump, you could have the car tuned for 87 octane gas. Not that I'd recommend that, because your power is going to drop drastically, but it's possible.

 

s/interesting/wrong/msi

 

I guess I should have gone further in the explanation.

Depends on application. Many of todays cars don't suffer from deceleration fuel consumption. Older non-fuel injected engines did and still do suffer from it.
Cars that were vacuum controlled versus CPU controlled today.
Although we are still trying to control deceleration use of gasoline without encountering the on/off hesitation that accompanies that control, and further the peak efficiency of the engine.

 

Your statement that more gas is consumed then compared to WOT still doesn't make any sense.

 

The savings is all in your head. Actually run the numbers and the time/energy spent on this thread, the map and the work will all be for not. Slower speed and lighter throttle will make a big real-world improvement

Run the numbers $5/gallon, 15K/year, 25 vs 30 mpg

25mpg = $3k gas spend yearly
30mpg = $2.5k gas spend yearly

Hardly worth a second review of this idea. To save money on gas you have to do things that cost you zero. IE driving at 70mph instead of 80.

 

Now this makes complete sense, because you increased your final drive gearing to lower RPMs. I gather Rod you fixed your speedo to read the correct speed.

 

No, I'm going by my gps. My speed-o is off by about 2.5 mph@70 mph with new 245/45-17 tires, and yes the difference goes down as the rear tires wear. So by the time their shot the difference in speed between an old 245/45 and a new 245/40 rear tire is now about 1.3 mph@70. I am one who would like to try 3.63 gears in my "S" because I know how to take a corner in a lower gear and still be able to put some miles on the car like when Cindy and I take one of our day drives(500 to 700 miles).
We have a 2300(5 day) mile drive coming up and when you can use the higher gears it would be nice to have them.

ROD

 

I'm getting around 27-29 with Direzza Z1-SS tires. I rarely get less than 300 miles a tank though.

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