Thoughts on the MPG Variance and Data Gathering

Having had my 2010 for long enough to realize that the days of the MFD closely resembling real world data is gone and still wondering why.

my thoughts; after preliminary examination of my mileage data, it seems that when i drove at a much higher speed which means less EV operation, less charging of the pack, etc. the MFD mileage variance was less.

now this observation is difficult because i dont drive at freeway speeds regularly enough to really track this well. so what i am doing now is adding a new column to my excel (actually use open office "calc"...which is just as good AND FREE) which is the "average speed" reading to see if this correlates.

on my tanks so far. only the "dealer" tank had higher readings on the MFD so that pretty much means the old days of the MFD being higher half the times and the pump being higher slightly less than half the times are gone...

my tanks so far;

miles.....MFD.....Pump
268.......57.8.....60.91 (dealer tank...ignore this)

614........62.......59.41 (includes one day 450 mile trip probably averaging close to 45-50 mph overall)

448.6......63.6.....53.81 (the imfamous "doorsill tank". this is tank that was reset in middle so its computed average before and after. this was pretty much no freeway driving that i remember or very little. i have a calendar that i use to plan family outings and there was nothing during this time)

622.9.....68.1.....62.4 (another tank that nothing really comes to mind as far as anything. on calendar, there was one trip to seattle RT about 110 miles... nothing else comes to mind.)

569.8......60.7...57.32 (this is the "Leavenworth" tank... granted you really have to have been following my posts to understand the names of these tanks but the trip was 350 miles and crosses two mountain passes which are over 4000 feet. probably the most impressive performance i have even seen in my 5+ years driving Pri's...average on this trip was 52 mph and was actually recorded on post i made here referencing regen)

so on the tanks above, the two tanks that were only a few mpg off had very long trips at highway speed in them. granted, all this is very prelim...

need more data, but with 3 cars in a two driver household, it will literally take months (average fill times is around 17 days)

anyone else notice something like this?

**EDIT**
07/30/20009 tank 516.3 miles 61.5 MFD, 53.44 pump...23 mph diff 8 MPG

notes ; most of tank was done during severest heat wave in Pacific Northwest history. more than a few times, i had the car sitting with AC blasting (i am almost in Pri with son) when i would have normally probably have parked in the shade with the windows open. AC KILLS the mileage when driving at street speeds. only a minor effect while on freeway.

 

i use Zenn for work commutes. Pri is really only used on my days off (have 3 a week!!) or when the family goes out. we used to use the SPM for that, but now the 2010 gets that role even on short trips... it just doesnt seem right to let a brand new car sit for 2/3rds of every week.

alfon; overfilling is not recommended. since i can easily do 600 miles on a tank, i dont feel the need to top off. the dealer tank was filled more than i fill so that is why the MFD reading was higher on the first tank, but i stop pretty much within a buck of the first click. besides, the issue is not tank fill consistency, if it were, i would occasionally get the MFD reading higher and that has never been the case and appears will never happen again unless the tank is not filled properly

now, on my last tank, my pump was malfunctioning, so it stopped at 3 gallons, which would have been 180 mpg... so i kept going since i knew the MFD reading said i should have more than 9 gallons. well it shut off 3-4 times before that point, so i kept going. ended up with around 9.7 or so.

 

what is your driving patterns? how far do you drive at one time and how fast do you drive?

if i am right, its mostly freeway and probably better than 30 miles one way

 

ok so trip still mostly freeway speed give or take. next time you fill up, note the average speed for your trip. granted this is not always a good indicator of the type of driving you do especially if in a situation where you spend a significant amount of time with car on but moving very little

 

well Wayne that could be as well, dont really have enough data, but the MFD mileage on tanks 2 and 3 only differ by 1.6 mpg but the pump reading differ by almost 6 mpg.

start tracking your average MPH for each tank. now granted, it could be off, mine is probably a bit low because a lot of times i be picking up my kid at grandma's and i frequently dont turn the car off. usually in and out in less than 5 minutes most of the time, so that would lower it. i should probably stop doing that at least for a while until i can get some more data gathered.

 

Costco is where i got the gas and although the state mandates pumps be calibrated every 3 years, Costco calibrates theirs every 6 months. they acknowledge that the mechanics of the pumping system do wear out and becomes inaccurate, so they take on the expense to go the extra mile to make sure the pumps are accurate.

the last time i went there which was last week for the SPM, i checked the their inspection stickers were dated 06/2009...

 

OP edited with latest tank. think i probably short-filled the previous tank which accounts for part of large discrepancy on this one. last tank shut off 3 gallons to early, so filled it to estimated level of fullness. lost first bar at around 80 miles i think which is far less than normal.