This is strange -- After filling up the tank today (on a nicely warm engine) I drove home about 20 miles and got 25 minutes worth of time on the bar graph. The tank MPG shown on the bottom of the consumption screen showed 58.5, yet all 5 bars were showing 50MPG or slightly above. Running an average across the 5 5 minute averages would suggest my MPG would have been about 50-52 tops. Anyone have a reasonable explanation of this behavior? Why would the average of 5 minute averages be over 5% different than the "instantaneous" overall average? Speaking of which -- does anyone know how the overall average is calculated? Does it just update every few seconds with the instantaneous mileage of that second and add that in to the previous average (i.e. if there have been "n" updates since the last reset so the calculation is something like this? New Average = [(Old Average * n) + Cur MPG]/(n+1) Thanks! Peter+
May be several things. Remember you're not averaging over time, only distance and gas used. Thus, one of the 50mpg 5 min graphs may have only represented a couple mile of driving where one of the higher rated 5 minute bars a much longer distance. The display at the bottom doesn't take time into consideration at all. Also, you had some distance traveled since the last 5 min bar popped up. In fact, you may have gone 4.5 minutes and there would be no bar pop up for that. If you'd averaged 60-65mpg during that last 4.5 minutes not represented on the bar graphs, esp. after a fresh fill up it could really push the overall mileage up. In fact, I find that usually the mpg over the very last part of a trip is the highest b/c it tends to be over slower roads (ie in a subdivision or side roads to work) rather than the hwy. or faster multilane roads.
The bars appear to round down to a multiple of 5mpg. Thus, 5 minutes of 59.5 appears as 55 on the chart.
1. my bars do not round up or down to any discernable figure. i have distinct readings that seem to vary by 2.5 mpg... 2. the difference in the tank reading and the average of the bar graphs is easily explained. suppose you drive 29 minutes. you average 50 mpg driving 10 miles average over first 25 mins. then you average 60 mpg over last 4 min driving 60 mph. you will still see the same 5 bars with the 50 mpg average... but your total tank mpg is updated more often and therefore will be much more accurate and should be the only thing you go by anyway. it is based on distance and gas used... the bar graph is based on time and therefore is VERY MISLEADING and should be used for comparision purposes only. so what would tank mpg be?? 57.6 mpg how do i come up with this?? lets look at gas consumed first 25 min... 50 miles @ 50 mpg = 1 gallon next 4 min.... 4 miles @ 60 mpg = .066 gallons total 54 miles using 1.066 gallons of gas = 57.59 mpg
as an afterthought try this... next time you fill up, make sure you reset your tank mileage and drive 5 mins. stop. record tank mileage and then just put in park and sit for at least 10 min. now you will have 3 bars, one with whatever your first 5 min produced and 2 others that should be close to zero. notice your tank mileage... didnt change did it?? (realize that if you have the air conditioning or heat blasting away, it might change) i once placed my car in park for 30 min (could have been more) once just to see what would happen.. (was waiting for a friend who had an appointment) the only thing i had going was the radio and after a full screen of zeros, my tank mileage didnt even change one-tenth of mpg.
How do you sustain 50mpg at 120mph? For that matter, how do you sustain 120mph in a Prius? Did you need to upgrade your tyres?
tms...Wth are you talking about?? listen, we have a member who has a legitimite question over a legitimite concern. if you have something CONSTRUCTIVE to add to the thread please do.
In your post, it sounded as if you were suggesting that the example had the driver going 50 miles in 25 minutes - ie a speed sustained of 120mph. I'm sure you were just using made up numbers to prove how the AVG can be quite different from the Consumption 5-minute interval display, but I think tms was just poking fun at you. -m.
i realize that... and maybe i be too harsh... but still ITS ONLY AN EXAMPLE... and people with feeble brains like me, i need numbers that are easy to crunch... that is why i picked them....can figure out in my head easier. you will notice the 4 minute segment was 60 mph which equals a mile a minute... another number picked purely for conveinence and nothing else. in the real world, i have documentation of getting nearly 70 mpg if driving that slow.
