Fuel Mileage Computation
09-27-2009, 12:28 PM
#1
Thread Starter
Join Date: Jan 2009
Location: MT
Posts: 28
Fuel Mileage Computation
I have an 05 V6. The onboard computer will tell you your average gas mileage. It will also tell you how many gallons you have burned since the last fill up. How does it determine this? Is there an actual transducer that the fuel flows thru like I have on my airplane and boat or does the computer figure it some other way?
09-28-2009, 03:27 PM
#5
5th Gear Member
Join Date: Oct 2005
Location: Southern California
Posts: 3,678
09-28-2009, 03:43 PM
#6
6th Gear Member
Calculating by hand is typically more accurate than using the on-board reading. Roughly 80-90% of those on the forum state that their on-board is often 1-2 MPG conservative compared to hand-calculated values. However, my g/f's '06 V6's on-board is nearly dead-on. It's been stated that the on-board uses injector pulses to calculate fuel mileage. Whatever it uses, I consider it less accurate than hand calculating using, at time of fill-up:
current odometer reading - previous odometer reading
# of gallons (per the gas station pump)
Hand calculation also assumes that both your odometer and the gas station's pump are accurate. The on-board is good for a relative reading in most cases. Additionally, if you're not hand calculating AND resetting your average MPG at each fill-up, you'll barely see those changes to your fuel economy that indicate something is amiss with the car (i.e., low tire pressure, poor fuel quality, clogged intake filter...).
current odometer reading - previous odometer reading
# of gallons (per the gas station pump)
Hand calculation also assumes that both your odometer and the gas station's pump are accurate. The on-board is good for a relative reading in most cases. Additionally, if you're not hand calculating AND resetting your average MPG at each fill-up, you'll barely see those changes to your fuel economy that indicate something is amiss with the car (i.e., low tire pressure, poor fuel quality, clogged intake filter...).
Last edited by Nuke; 09-28-2009 at 03:45 PM.
09-28-2009, 06:15 PM
#7
2nd Gear Member
Join Date: Feb 2009
Location: FL
Posts: 157
Calculating by hand is typically more accurate than using the on-board reading. Roughly 80-90% of those on the forum state that their on-board is often 1-2 MPG conservative compared to hand-calculated values. However, my g/f's '06 V6's on-board is nearly dead-on. It's been stated that the on-board uses injector pulses to calculate fuel mileage. Whatever it uses, I consider it less accurate than hand calculating using, at time of fill-up:
current odometer reading - previous odometer reading
# of gallons (per the gas station pump)
Hand calculation also assumes that both your odometer and the gas station's pump are accurate. The on-board is good for a relative reading in most cases. Additionally, if you're not hand calculating AND resetting your average MPG at each fill-up, you'll barely see those changes to your fuel economy that indicate something is amiss with the car (i.e., low tire pressure, poor fuel quality, clogged intake filter...).
current odometer reading - previous odometer reading
# of gallons (per the gas station pump)
Hand calculation also assumes that both your odometer and the gas station's pump are accurate. The on-board is good for a relative reading in most cases. Additionally, if you're not hand calculating AND resetting your average MPG at each fill-up, you'll barely see those changes to your fuel economy that indicate something is amiss with the car (i.e., low tire pressure, poor fuel quality, clogged intake filter...).
09-28-2009, 10:35 PM
#8
Thread Starter
Join Date: Jan 2009
Location: MT
Posts: 28
Calculating by hand is typically more accurate than using the on-board reading. Roughly 80-90% of those on the forum state that their on-board is often 1-2 MPG conservative compared to hand-calculated values. However, my g/f's '06 V6's on-board is nearly dead-on. It's been stated that the on-board uses injector pulses to calculate fuel mileage. Whatever it uses, I consider it less accurate than hand calculating using, at time of fill-up:
current odometer reading - previous odometer reading
# of gallons (per the gas station pump)
Hand calculation also assumes that both your odometer and the gas station's pump are accurate. The on-board is good for a relative reading in most cases. Additionally, if you're not hand calculating AND resetting your average MPG at each fill-up, you'll barely see those changes to your fuel economy that indicate something is amiss with the car (i.e., low tire pressure, poor fuel quality, clogged intake filter...).
current odometer reading - previous odometer reading
# of gallons (per the gas station pump)
Hand calculation also assumes that both your odometer and the gas station's pump are accurate. The on-board is good for a relative reading in most cases. Additionally, if you're not hand calculating AND resetting your average MPG at each fill-up, you'll barely see those changes to your fuel economy that indicate something is amiss with the car (i.e., low tire pressure, poor fuel quality, clogged intake filter...).
I hope the computer is a little conservative. I'm getting an indicated 23 mpg in the city. I'll have to do some hand calculations to verify.
09-29-2009, 05:48 PM
#9
3rd Gear Member
Join Date: Apr 2009
Location: WI
Posts: 773
I drive about 50/50, city/highway, 25 minutes each way to work. I reset the onboard at each fill-up (odometer, MPG, and fuel used) mine is always between 23.3 and 24.2 mpg. I've checked it with paper and pencil a few times and its always been nearly dead on.
