Adair Posted February 12, 2013 Report Share Posted February 12, 2013 (edited) between *gallons used* in your Summary and gallons bought at the pump? Example: At my last fill up, car said I had used 8.99 gal. but the pump said I bought 9.35 gal. Dang! I never paid any attention to this stuff before! What's happened to me? Edited February 12, 2013 by Adair Jus-A-CMax 1 Quote Link to comment Share on other sites More sharing options...
dtorres Posted February 12, 2013 Report Share Posted February 12, 2013 Same thing happens to me. Someone else on this forum figured it and determined that the car calculated average mpg were off by a consistent percentage. Don't recall what that percentage was though. Quote Link to comment Share on other sites More sharing options...
Jus-A-CMax Posted February 12, 2013 Report Share Posted February 12, 2013 (edited) between *gallons used* in your Summary and gallons bought at the pump? Example: At my last fill up, car said I had used 8.99 gal. but the pump said I bought 9.35 gal. Dang! I never paid any attention to this stuff before! What's happened to me? :redcard: You tanked up at 8.99 gallons, you've barely over half tank there Adair, you still have a minimum 140 miles before you fume out ;) Yeah, I noticed it a long time ago, I'm no engineer so it is what it is...which is why fuelly says one thing and my screen shots says another. Both accurate from their own perspective and I don't have money or time to stick gauges into my car that I know nothing about...jus' sayin. Edited February 12, 2013 by Jus-A-CMax Quote Link to comment Share on other sites More sharing options...
Adair Posted February 12, 2013 Author Report Share Posted February 12, 2013 :redcard: You tanked up at 8.99 gallons, you've barely over half tank there Adair, you still have a minimum 140 miles before you fume out ;) I know, I'm a wimp. Actually, I was trying for a fill up on a nicer weather day, when I could wash the car............ok, so, I'm still a wimp I like my screen summary better than Fuelly. Quote Link to comment Share on other sites More sharing options...
darrelld Posted February 12, 2013 Report Share Posted February 12, 2013 between *gallons used* in your Summary and gallons bought at the pump? Example: At my last fill up, car said I had used 8.99 gal. but the pump said I bought 9.35 gal. Dang! I never paid any attention to this stuff before! What's happened to me? I am not sure the capless system fills are as consistent as the regular capped. I can go to any RaceTrac and I can't fill beyond 3/4 of a tank with using the slowest fill rate, this is below what you can lock the handle in. If I go to our new Costco the pump nozzle is slightly smaller diameter and fills all the way without any problem. Quote Link to comment Share on other sites More sharing options...
Jus-A-CMax Posted February 13, 2013 Report Share Posted February 13, 2013 I know, I'm a wimp. Actually, I was trying for a fill up on a nicer weather day, when I could wash the car............ok, so, I'm still a wimp I like my screen summary better than Fuelly. Well you have a very pretty and full Jelly Bean today :) & :rockon: Quote Link to comment Share on other sites More sharing options...
RedLdr1 Posted February 13, 2013 Report Share Posted February 13, 2013 between *gallons used* in your Summary and gallons bought at the pump? Example: At my last fill up, car said I had used 8.99 gal. but the pump said I bought 9.35 gal. Dang! I never paid any attention to this stuff before! What's happened to me? What has happened to you? That's easy, you are coming down with a early case of the Hypermiler disease... ;) Suddenly silly stuff "matters" in the quest for the best MPG numbers! :) Your car said you used 8.99 Gallons and you pumped in 9.35 Gallons....that is a variance of only 4%... The car and gas pump are not synchronized. And you cannot fill the gas tank to the exact same point every time even if you use the same pump every time as there are too many variables. That 4% variance is actually pretty darn good... Quote Link to comment Share on other sites More sharing options...
Adair Posted February 13, 2013 Author Report Share Posted February 13, 2013 Well you have a very pretty and full Jelly Bean today :) & :rockon: And she was turning heads in Ann Arbor today too! :camera: :wub2: my car!What has happened to you? That's easy, you are coming down with a early case of the Hypermiler disease... ;) Suddenly silly stuff "matters" in the quest for the best MPG numbers! :) Your car said you used 8.99 Gallons and you pumped in 9.35 Gallons....that is a variance of only 4%... The car and gas pump are not synchronized. And you cannot fill the gas tank to the exact same point every time even if you use the same pump every time as there are too many variables. That 4% variance is actually pretty darn good... Hmmm, hypermiler's disease? Sounds serious! What are some other symptoms? The technician at my dealership last week said my screen name should be MPG-OCD :drool:Just curious, should I have filled up what my car said? 8.99 gal? That would not be *full* right? Ok Redldr1, I won't sweat the 4%. Thanks guys! hybridbear 1 Quote Link to comment Share on other sites More sharing options...
Jus-A-CMax Posted February 13, 2013 Report Share Posted February 13, 2013 Best practice is to set the flow rate on the "low" flow latch and don't top up. Doesn't pump as fast but like hybrid driving, you trade time for something else. You're good to go :) Adair 1 Quote Link to comment Share on other sites More sharing options...
roninsd Posted February 13, 2013 Report Share Posted February 13, 2013 Hmmm, hypermiler's disease? Sounds serious! What are some other symptoms? The technician at my dealership last week said my screen name should be MPG-OCD :drool: Coming to this forum every day (sometimes more than once) to see what's up with your fellow maximizer, and getting excited about what others are saying about their cars and mileage -- and the sickness spreads! Adair 1 Quote Link to comment Share on other sites More sharing options...
MSmith1915 Posted March 4, 2013 Report Share Posted March 4, 2013 I just accept the fact that the car gallons and pump gallons are not going to be the same. So, for 3 or 4 fill ups, I fill up to what the car says I used. That way my MPG will be the same as what the car calculates. Then, after 3 or 4 fill ups, I'll use about 2 gallons of gas and then top off until the pump clicks to a stop. Usually it's about 1 gallon more than what the car display says. The MPG is pretty low but it's over a small sample of miles, maybe 80 to 100 miles and wont skew your total mileage very much. Quote Link to comment Share on other sites More sharing options...
Generalbeluga Posted March 8, 2013 Report Share Posted March 8, 2013 Interestingly enough, my mileage as stated by the car's computer matches the Fuelly MPG calculation to within 1/10 MPG! All I do is go to COSTCO, set the pump delivery rate on high, top it off twice after if auto stops and Walhalla, it is accurate to the Fuelly figures! Quote Link to comment Share on other sites More sharing options...
wab Posted March 8, 2013 Report Share Posted March 8, 2013 The last 6 or 7 cars we've had have tried to calculate MPG, NONE were successful.ALL reported better mpg than I hand calculate, and I hand calculate every time and keep a log. I've seen the statement on other forums that"you cannot fill the gas tank to the exact same point every time even if you use the same pump every time as there are too many variables." Which means that some of the time you'll put less gas in than the car says you used.But my logs show that about 1 out of 10 fills show the same mpg as the car reports.AND about 1 out of 10 fills show higher mpg than the car reports. The other 8 show less mpg than the car reports. Quote Link to comment Share on other sites More sharing options...
Edsel Posted May 13, 2013 Report Share Posted May 13, 2013 (edited) My Fuelly number is 39.0 MPG, but my car since starting Fuelly says 40.8 MPG. I figured the car would be optimistic, but not by this much. Does this seem too optimistic? Edited May 13, 2013 by Edsel Quote Link to comment Share on other sites More sharing options...
JAZ Posted May 13, 2013 Report Share Posted May 13, 2013 I've recorded several fillups where the pump recorded 8% more fuel than the vehicle reported. Like wab, I've had a couple fillups use 1% less than reported, but overall the vehicle reports better mileage than the fuel pump. Conversely, the odometer reads about 1.5% low. Quote Link to comment Share on other sites More sharing options...
Jus-A-CMax Posted May 13, 2013 Report Share Posted May 13, 2013 My Fuelly number is 39.0 MPG, but my car since starting Fuelly says 40.8 MPG. I figured the car would be optimistic, but not by this much. Does this seem too optimistic?Don't even sweat this one, IMO. The MPG number comprises of 2 components, #miles / fuel used. Even the slightest change in the bottom denominator such as a wee bit top off, I have seen changes from a 51 MPG to a 47 MPG. Same goes for short trips, one squirt of ICE can change a 40+ to a mid/high 30s...its devastating :cry: ;) For me, after 13,500+ miles my fuelly and my lifetime MPG is about 0.3 or thereabout diff. If I have to believe either fuelly or lifetime, I'll pick the car, its the most consistent unit for measurement vs the variations across fuel pumps. My 2c. Quote Link to comment Share on other sites More sharing options...
SnowStorm Posted May 15, 2013 Report Share Posted May 15, 2013 Then I wonder if pure gasoline versus 10% ethanol (E10) makes any difference to the comparison. "The government" says E10 gives 3 to 4% less mileage.( http://www.fueleconomy.gov/feg/ethanol.shtml ). But I don't know if the car's computer compensates for the difference. Quote Link to comment Share on other sites More sharing options...
hybridbear Posted May 22, 2013 Report Share Posted May 22, 2013 Then I wonder if pure gasoline versus 10% ethanol (E10) makes any difference to the comparison. "The government" says E10 gives 3 to 4% less mileage.( http://www.fueleconomy.gov/feg/ethanol.shtml ). But I don't know if the car's computer compensates for the difference.The car is measuring your actual fuel used. But it likely is only measuring the fuel that passes through one injector and then multiplying it. That is the source of the discrepancy Quote Link to comment Share on other sites More sharing options...
Recumpence Posted May 22, 2013 Report Share Posted May 22, 2013 My last fillup showed 12.88 gallons used on the dashboard and 13.1gallons at the pump. Matt Quote Link to comment Share on other sites More sharing options...
salsaguy Posted June 6, 2013 Report Share Posted June 6, 2013 I'm sure most car mfgs use a more optimistic mpg value on the dash as they figure most folks are too lazy or too high tech to be hand calculating (checking) the numbers, and want the owners to think they are getting better mpg than they actually are. if they don't hand check they will never know. Also im sure there is a limit to how far off they are allowed to be off. i think 5% may be within the allowable limit but only they know. Also if you are using fast fill pump method to fill your tank you are creating turbulent flow in the tank which can take a while for the gas level (sensor) to settle down so it may click off too soon/or too late to be accurate.best method is to fast pump for the first 85% of the fill uo then slow fill the last bit (to let it settle down) till it clicks off and DON'T top off.I'm sure your numbers will be better / more accurate and more consistent that way.less variation is always better.this is why c fuelly.con numbers are all over the place. method of fill has a lot to do with it and what you're calculated mpg will be.and I'm wondering how many fuelly members use the dash info instead of the hand calculated info to get their avg mpg numbers Quote Link to comment Share on other sites More sharing options...
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