Yes, my truck is about 70/30 highway / city
I'm not a math whiz either, but you're not computing mileage right.
Forget about the 22.5 gallons. The only way that number is useful for figuring mileage is if you burn every drop in the tank. Also, don't use your fuel level needle as a measurement...it's not accurate for determining mileage. All it tells you is roughly how full or empty the tank is.
Here's what you need to do step-by-step:
-Step 1: When you fill up, reset your trip odometer.
-Step 2: Drive until you need to fill up again. When you fill up again....make sure you write down what the pump tells you
on how many gallons you just put in, say 18.53 gallons for example. If you think about it, putting 18.53 gallons in since your last fillup is the same as saying you've burned 18.53 gallons since your last fillup, know what I mean?
-Step 3: Before you leave the gas station, look at your trip odometer. Take the number of miles you drove since your last fill up, say for example 290 miles. Divide it by the number of gallons you just put in, which we already said was 18.53.
Answer: 290 divided by 18.53 = 15.65 MPG
You don't even have to be anywhere near the empty line for your second refill for this method to work. You could do it a half tank or even 3/4 of a tank if you want...just as long as you know how many miles you have driven since the tank was filled and how many gallons you've burned (i.e. by looking at how many gallons you put in on the second fillup).
If you want really good mileage, perhaps selling the X and buying a honda civic would be a good option. The 2010 civic gets 35 MPG or better EASY with 50/50 highway/city driving even when it's completely stock and driven with a heavy foot.
ok here is what I've done...
I have ran the tank to the line at the very bottom of the indicator... right next to empty... at this point I show around 300 mile; this is what I assumed correct since I've done it several times... like this, 300/22.5=13.33
Also, I've done:
fill up the tank, note miles at full, 3/4 full, 1/2 full and 1/4 full... for some reason gas seems to last longer while trying to use the first 1/4 tank (from full to 3/4 full).... at the 3/4 full indicator, milage is about 100 miles... like this total milage would be 400 miles => 400/22.5=17.78 mpg.
Also, I've done:
Take note of the miles at tank 3/4 empty... miles=270 (or so)... I do something like x=(22.5x270)/16.875=360miles on a full tank => 360/22.5=16mpg.
so maybe take the average? (13.33+17.78+16)/3=15.70mpg?
ump! too much math... that is what has mee confused... my little brain does not compute #s.