Hi All:

___I always use total gallons from the pump and miles from the odometer for all my tank entries. The odometer is your legal mileage and the pump is a legally regulated system. It may not be exact but filling up from almost empty to the filler neck for years, most pumps match about what I would have expected … The various FCD displays in our automobiles are not a legal record by any stretch.

___The following is in regards to AH NAVI owners as that is where the whammo-dyne TC/FCD display is

___I know Tink uses the NAVI units calculations in his AH saying it is more precise then the odometer and I tend to disagree. Unless the NAVI unit is completely booted and has a hold of at least 3 solid birds, it doesn’t know where the heck you are all the while you are tooling down the road. I see this every morning when leaving my home and for that first 45 seconds or so, it is registering me in the middle of my subs lake or on the other side in another section. I have breadcrumbs enabled and see the error induced with a short amount of travel through my subs lake and fields etc. When leaving work on a non-digitized road, the breadcrumbs are stacking up and although they do overlap, they are also spreading out. In other words, they do not fall on top of one another even though I am traveling down the one and only road available … This is not just the std. < 15’ of error that the GPS units hold but real error of maybe 20’ at its worst after tens of entry/exits. I will take a pic someday to show this. Whenever you do not follow a particular pre-planned route, the NAVI will override your true travel route for a few seconds with its built in/programmed in “Snap to Road” feature and once it finally figures out you are going straight instead of following its direction as an example, it will “Snap to Road” (the one you are really on) and you continue on its merry way. Whenever the GPS is slightly off, it may have you traveling on an access road vs. the Interstate. I have only seen this once so far but again, the GPS unit finally figures out that you are 15’ over and it snaps to road (the Interstate) and once again adds another small bit of error. The GPS units are to imprecise even if the digitized roads are dead on imho. The Honda OEM NAVI’s are tied to the car in the case the GPS unit loses track but only for a short period. I do not think the system takes the track into account when it supposedly does have a lock or is originally seeking one during or just after boot …

___I also keep a log of the FCD’s vs. the actuals on the cars that have them but only report the legal calc’s myself. The Insight’s FCD was very close to its actuals on almost every tank with usually < a .5% delta between the two. With a vapor recovery fill, it would show a huge discrepancy to the downside and to the upside on the next regular tank fill (75 mpg calculated vs. FCD = 105 and on the next std. fill would show a 105 with the hand calcs at 135 as an example). When this happened, I would average the two tanks and it would almost match up the FCD display for both tanks once again. Look at the “Achievement Record’s” tank of the Insight at just 106 due to a 2 tank averaging as an example when the record tank - actual was up around 109.0. The lmpg display of the Insight was usually dead on. Dead on overall as there was a small period when the display would update with its normal .2 or .3 jump. The LMPG was registering 92.5 mpg for a touch over 2,000 miles and my calc’s were 92.5 mpg as well. Its final trip at 103.1 over 1,032 miles brought up the calc’s from 92.454 to 92.767 mpg but the lmpg FCD display had not yet locked in 92.8 … Another 300 - 500 miles of highway would have locked it in I am sure.

___I do not know if the HCH’s, Prius II’s, Escape HEV’s, or RXh’s can be recovery filled like the Insight could be so it is really a moot point if they cannot.

___Here is a short compilation of the distance and FE errors produced over 7 tanks in the PZEV Accord w/ NAVI in case anyone is interested:

“Odometer” vs. “NAVI display”

Miles traveled

789.4 - 788.5
860.6 - 859.0
767.2 - 766.3
829.0 - 828.4
802.9 - 802.2
833.3 - 832.3
859.8 - 857.9

”Odometer and Pump calculated” vs. “NAVI display”

MPG

42.519 - did not record
45.362 - 44.3
44.894 - 44.3
44.707 - 44.0
44.374 - 43.2
45.315 - 44
46.270 - 44.7

___Because I am forcing more Auto-stops now given the traffic nightmares I have seen this week, the discrepancies will only grow given the NAVI’s inability to boot immediately while I am slowly accelerating and/or decelerating in stop and go traffic jams after a reboot.

___With all of the above, the odometer and pump is the only “legal” way to calculate one’s FE imho.

___Good Luck

___Wayne R. Gerdes
___Waynegerdes@earthlink.net