You present a fine example to demonstrate the "interval fuel economy calculating trick", Bob.

200 miles @ 83.6 mpg -> 2.39 gal fuel used
250 miles @ 79.4 mpg -> 3.15 gal fuel used

Thus 0.76 gal were used during the last 50 miles -> 65.8 mpg on that stretch. Left as exercise for readers: perform similar calculations on Bob's recovery efforts.

DAS

 

Apparently you didn't read down to post #9 in this thread. It was worse than before. But hey, I really appreciate your calculations. Please calculate for me/us the damage described in post #9 of this thread, and my recovery efforts to date.

Today, as I sit, he has had no more drive time, and I am at 75.7 mpg at 705.3 miles.

Thanks, Bob

 

After 382 miles, you were at 69.6 mpg. This means 5.49 gal were consumed.

115 miles earlier, you were at 267 miles and 80.2 mpg. This means 3.33 gal were consumed at this point.

Also, it means that 2.16 gal were used for the final 115 miles. This gives a fuel economy of 53.2 mpg. Your son is already beating the EPA numbers.

What is the error in your display?

 

Actually, for the last several thousands of miles, my display usually reads dead-on or 2 or 3 mpg lower than the actual calculated mpg.

It is gratifying to know that my son is beating the EPA numbers, especially with all of the stop and go he did and idling without autostop, but 53 mpg for 115 miles sure puts a beating on a 83 mpg tank.

BTW, has anyone calculated the mpg of my recovery efforts? I suppose I could do it myself, but I was a history major and haven't taken a math course in 32 years! (I am sorry for dumping on my history degree again, but my law degree pays my bills so I have a hard time dumping on it. )

 

Here goes:
After 382 miles, you were at 69.6 mpg. This means 5.49 gal were consumed.
(382 miles divided by 69.6 miles per gallon equals 5.49 gallons)

After 705.3 miles, you were at 75.7 mpg for a total of 9.32 gallons used.

Take the differences to get 323.3 miles and 3.83 gallons for a fuel economy of 84.4 mpg.

Not too shabby.

 

Attempting this higher math on my own...today I went to the office, 2 courts, back to the office and then back home. It was a round trip of 92.4 miles, and at the end my trip meter reads 797.7 miles and 76.8 mpg (10.3867 gallons). Subtracting Mr. Kite's previous calculation of 9.32 gallons I calculate that I used 1.0667 gallons over the 92.4 miles, for an interval FE of 86.62 mpg. Am I doing this right?

 

Those are the same numbers I get. It looks like you can do this advanced math after all.

 

Well, I finished that tank on Thursday at 1,159 miles at 78.7 mpg calculated (77.9 displayed) for the whole tank (14.72681 gallons). After 382 miles of aggregate driving, my son's driver training had driven my tank display down to 69.6 mpg from the 83.6 mpg when he took over.

My recovery efforts over the 777 miles since my son last drove required 9.23681 gallons for an average of 84.1 mpg to get my 83.6 mpg tank to recover from my son's driver training of 69.6 back up to the 78.7 aggregate.

 

My oldest is almost 13 years old so he has some time left before driving but still notices everything I do. With that said I'm not putting as much effort into hypermiling as when I'm solo.

Last month while we were on the way home from a store he asked me why I don't drive like everyone else. I explained that I fill my tank about every 10-12 days and it costs around $40, and if I drove like everyone else that would almost double.

I'm teaching him that all actions have consequences and fuel economy is no exception. At the time of this conversation we were alone on a 55MPH single lane rural country highway going about 42-43MPH. I pointed out my FCD and showed him the upper 60's figure and what that meant, and if we would have chosen the 70 limit freeway it would be low-mid 50's at best- and more frequent fill ups.

These kind of lessons aren't usually taught in drivers education and it's our responsibility to let them know.

-Steve

 

You will be suprised what you can teach a child. My little guy is six and we turn off certain things by the power strip. (EX. computer, Audio/Video system, etc.) Along with compact flourescent lights I have one bill hit the $40's and that was because the heat was let on in my son's rooms for part of the month. My last two elevtric bills were $11 and $14 a little effort goes a long way.

He also understands that the map car (HCH) gets better gas mileage than my Scion XB. And that my red car (AWD turbocharged Talon<---not Earth friendly but it's a blast to drive 18-19mpg 4 cylinder) gets really crappy gas mileage but is fast.