Originally Posted by Norma stitz

One of my pet peeves is when people say they ran a tank empty to check the mileage. Really? You ran out of fuel on your truck, called a tow truck, refueled and somehow got it started again just to see what your mpg was? That's not how to calculate mileage. Here's how to calculate mileage, and it's the only way.
First you must determine your odometer error. We all have one. Doesn't matter what your speed says, it's only the odometer reading we are after. Don't assume the error in speedo is the same for odo. They sometimes are wacky.

Use gps app on your phone and set it to tell you distance driven.
Record odometer trip meter miles and actual gps miles.
Divide odometer miles by actual gps miles. This is the percentage that your odometer is reading. If it's less than 1 you likely have oversize tires.
Subtract that number from 100. This is your percentage of error.
Multiply the error by your next "tank" odometer reading. Then add that back to the odo reading. This is your actual miles driven.
Divide by gallons used. This is your MPG.

So, for me with 35" tires I take my miles indicated, let's say 10 miles on trip meter while using my gps which indicates I actually travelled 10.8. That comes to .926. Subtract from 100 and you'll get .074. Or, 7.4% odo error. Now keep that handy for the next few tanks of fuel. Odo reads 325x.074= 24.05 miles error. Combine to tank and see that we actually went 349.05 miles. Divide by fuel pumped back in to top, and we get 13.96 mpg.
There might be different ways to use the same math, or maybe a shortcut here and there but that's the way to do it, as accurately as is practical.

You need to do it over several tanks, because city vs hiway, wind, mountains, or truck loads will skew results.

Originally Posted by Norma stitz

One of my pet peeves is when people say they ran a tank empty to check the mileage. Really? You ran out of fuel on your truck, called a tow truck, refueled and somehow got it started again just to see what your mpg was? That's not how to calculate mileage. Here's how to calculate mileage, and it's the only way.
First you must determine your odometer error. We all have one. Doesn't matter what your speed says, it's only the odometer reading we are after. Don't assume the error in speedo is the same for odo. They sometimes are wacky.

Use gps app on your phone and set it to tell you distance driven.
Record odometer trip meter miles and actual gps miles.
Divide odometer miles by actual gps miles. This is the percentage that your odometer is reading. If it's less than 1 you likely have oversize tires.
Subtract that number from 100. This is your percentage of error.
Multiply the error by your next "tank" odometer reading. Then add that back to the odo reading. This is your actual miles driven.
Divide by gallons used. This is your MPG.

So, for me with 35" tires I take my miles indicated, let's say 10 miles on trip meter while using my gps which indicates I actually travelled 10.8. That comes to .926. Subtract from 100 and you'll get .074. Or, 7.4% odo error. Now keep that handy for the next few tanks of fuel. Odo reads 325x.074= 24.05 miles error. Combine to tank and see that we actually went 349.05 miles. Divide by fuel pumped back in to top, and we get 13.96 mpg.
There might be different ways to use the same math, or maybe a shortcut here and there but that's the way to do it, as accurately as is practical.

You need to do it over several tanks, because city vs hiway, wind, mountains, or truck loads will skew results.

Originally Posted by 04badford

ARG , wouldn't be easer to just run it out of fuel , lol, all that Math brought back a head Trama from my old School math teacher , I followed my Scan Gauge reading it seemed purdy consistent except mountain passes , running higher Cetain fuel was the best on Mpg and it seem to get better miles per the buck.

Originally Posted by Norma stitz

"seem" being the operative word there.
My system scan tool, the torque app, thinks that my mpg is around 4-5 so I'm not going to give those things much credit for accuracy.

oh and to answer your question, no, it wouldn't because you still need to determine your odometer error to know how far that tank got you before sputtering to a halt on the side of the freeway.

i had a co worker once tell me that his car got great mpg for the first half of his tank but the second half was terrible, as evidenced by the needle. So he just kept it above half full all the time. I had to just walk away lol.

Originally Posted by Fuzzpuss

04badford, are you running all synthetic fliuds? Have you tried a higher temp thermostat like the Mishimoto 202 degree? Some guys have reported gains with these mods.

Also, you might want to remove the calipers and see if the guide pins are seized. That could put constant additional friction between the pads and rotors. Autozone has a cheap replacement kit if needed: Duralast Brake Caliper Bolt/Guide Pin-Rear H15051 - Read 1 Reviews on Duralast #H15051