mtnsubie Posted June 2, 2005 Share Posted June 2, 2005 I was wondering how accurate your in-dash MPG gauges are? I tested mine once comparing to the gallons filled to top off the tank divided by miles, and it seemed fairly accurate. What are you boys getting out there? Link to comment Share on other sites More sharing options...
VXCL Posted June 2, 2005 Share Posted June 2, 2005 i always do the math when i fill up and it is almost dead on everytime. the most it was ever off is 1mpg. i find thatvif you keep reseting your trip its more accurate vs when you compare to say the b trip which keeps counting and gives a super overall mpg not just since your last fill. on the highway i've been getting 26-26.5 reg driving like 20-21 MAYHEM #122/22 STS NNJR SCCA AUTOX4U.COM XENON RETRO GUIDE Link to comment Share on other sites More sharing options...
rallispec Posted June 2, 2005 Share Posted June 2, 2005 within 1 mpg Link to comment Share on other sites More sharing options...
canis Posted June 2, 2005 Share Posted June 2, 2005 Mine's more like 2-2.5 off. Link to comment Share on other sites More sharing options...
TSiWRX Posted June 2, 2005 Share Posted June 2, 2005 ^^^^ +1 with VXCL (although not his mileage figures) and rallispec - per their "accuracy" I, too, find as with VXCL that the shorter the mileage span, the more accurate the measure. I tend to keep Trip A as my tank-per-tank reset. -A <-- I love Winky, my "periwinkle" (ABP) LGT! - Allen / Usual Suspect "DumboRAT" / One of the Three Stooges '16 Outback, '16 WRX, 7th Subaru Family Link to comment Share on other sites More sharing options...
rts Posted June 2, 2005 Share Posted June 2, 2005 I just checked my mileage on a 700 mile trip. One tank was almost dead on, one tenth MPG difference, the second tank 1/2 MPG off. Averaging the two I'm less than a half mile per gallon off between the computer and the old math way. I have the 2.5i base engine and run around 30-31 mpg highway and about 21.5 city. The average for my past 2500 miles is 27.5 Link to comment Share on other sites More sharing options...
gfxdave99 Posted June 2, 2005 Share Posted June 2, 2005 Doing a fill tank to the top, reset trip odo, drive, fill tank to the top.. take trip/devide method shows about 1mpg less then the display If everything seems under control, you're just not going fast enough. - Mario Andretti Link to comment Share on other sites More sharing options...
kenzo Posted June 2, 2005 Share Posted June 2, 2005 Actual is 5-10% less than the displayed readout. This error has been consistent from delivery to now (18,000 miles). I generally get about 23 mpg and the readout is usually around 24.5 mpg. Link to comment Share on other sites More sharing options...
bemani Posted June 2, 2005 Share Posted June 2, 2005 About 1 mpg too optimistic. Link to comment Share on other sites More sharing options...
Ken S Posted June 2, 2005 Share Posted June 2, 2005 What would explain the difference people are observing between calculated and displayed mpg? Any thoughts? Ken Link to comment Share on other sites More sharing options...
kanoswrx Posted June 2, 2005 Share Posted June 2, 2005 Yeah I would say 1-2 mpg optimistic Link to comment Share on other sites More sharing options...
bemani Posted June 2, 2005 Share Posted June 2, 2005 What would explain the difference people are observing between calculated and displayed mpg? Any thoughts? Ken When they can't even get the fuel gauge to read correctly, how can they accurately monitor mileage??? Link to comment Share on other sites More sharing options...
kenzo Posted June 2, 2005 Share Posted June 2, 2005 Three basic operations have to happen accurately for an accurate MPG result: 1) Measurement of distance traveled - my odometer seems to be within 5%, based on 'reference' mile markers, although I don't know for sure whether the same sensor is used for MPG calculations. 2) Measurement of fuel consumption - don't know how accurate this is and don't know a good way to find out. 3) Division of distance/consumption - let's hope they got the trip computer software right and can divide without significant resolution or truncation errors. Link to comment Share on other sites More sharing options...
deneb Posted June 2, 2005 Share Posted June 2, 2005 My trip computer is consistently 1 - 1.5 mpg off as well. Link to comment Share on other sites More sharing options...
f1anatic Posted June 2, 2005 Share Posted June 2, 2005 300 miles to Detroit over the Memo Day Wknd. @ speeds 75-100 mph 27 mpg with the trip computer 26.3 mpg by dividing miles (292) over gallons (11.1) Link to comment Share on other sites More sharing options...
awdG35killer Posted June 2, 2005 Share Posted June 2, 2005 mine is always +1mpg. so it shows 22mpg but its really 21 mpg. Link to comment Share on other sites More sharing options...
Unilat Posted June 3, 2005 Share Posted June 3, 2005 I have a spreadsheet linked at http://www.calvars.com/unilat/auto/subaru/menu.htm that includes actual / computer mpg variance on the second tab. In a nutshell, in 31 fillups the computer averages out to about .75 mpg (3.5%) higher. Link to comment Share on other sites More sharing options...
CFar Posted June 3, 2005 Share Posted June 3, 2005 Mine's more like 2-2.5 off. +1 Link to comment Share on other sites More sharing options...
kenzo Posted June 3, 2005 Share Posted June 3, 2005 I have a spreadsheet linked at http://www.calvars.com/unilat/auto/subaru/menu.htm that includes actual / computer mpg variance on the second tab. In a nutshell, in 31 fillups the computer averages out to about .75 mpg (3.5%) higher. You need a hobby. (But seriously, nice work, thanks for the link!) Link to comment Share on other sites More sharing options...
iyamdman Posted June 3, 2005 Share Posted June 3, 2005 OMG (Only Midwest Gas) you can buy premium for less than $2.50!!! In SoCal - prices are starting to drop, and I can get the cheepest premium (ARCO) for about $2.56 right now - 3 weeks ago I paid $2.81 (Union 76). On my spreadsheet, my meter of about 2-3% higher than calculation. Link to comment Share on other sites More sharing options...
warnoldscu Posted June 4, 2005 Share Posted June 4, 2005 I was going to say that if you had replaced your tires with a new overall diameter then there would be some difference on your odometer and speedometer... but then again, when you checked the car with your calculator, you would be using the same numbers unless the MPG estimator actually uses different sensors to measure difference like someone said above. In that case it could be entirely possible that the MPG calculator is more accurate than the manual calculation if the manual calculation was taken off of the slightly innaccurate odometer..... anyone know how the estimator works exactly? Link to comment Share on other sites More sharing options...
Unilat Posted June 4, 2005 Share Posted June 4, 2005 You need a hobby. (But seriously, nice work, thanks for the link!) :lol::lol::lol: I have to use my PDA for something! Link to comment Share on other sites More sharing options...
len Posted June 5, 2005 Share Posted June 5, 2005 I have 1230 mi. on the odometer. The driving is 70% city and 30% highway. Trip computer shows 21.6 MPG my calculation is 22.9 MPG. So computer is off by more then one MPG. However I did not reset it. Maybe there is a difference. Link to comment Share on other sites More sharing options...
DKB_SATX Posted June 5, 2005 Share Posted June 5, 2005 What would explain the difference people are observing between calculated and displayed mpg? Any thoughts? Ken I suspect from observation that the computer doesn't include time you're not moving in its calculations. While the car is sitting there burning fuel, the computer is ignoring that use of fuel. I have no basis for this suspicion other than watching the behavior of the average MPG readout's behavior. DKB Link to comment Share on other sites More sharing options...
jt51 Posted June 5, 2005 Share Posted June 5, 2005 On my trip computer, the "remaining miles to fill up" never goes higher than 250. Is this the limit? Because, when I fill up; reset, get on the highway, it should read well over 300 miles, when my AMG is over 20. Link to comment Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.