I was trying to figure out what seemed to be going with my data at voltstat.net (my MPG CS keeps dropping even though there is no CS usage). After seeing what Mike is doing I wanted to understand why/how its wrong.
So I pulled all my gas purchase logs (and checked with the dealer on their usage, it had ~100 miles when we bough it) and still could not make it work out.
Yesterday while reading an older edmunds post about the prius and others in their fule sipper tests I saw the following:
.... the onboard fuel economy gauges also differed from reality. While the others ranged from 1 mpg better than reality to 3 mpg worse, the Toyota Prius was woefully inaccurate. On the back-road route, the Prius' computer claimed it was getting 6.8 mpg (14 percent) better than it actually was, while the city yielded a 5.4-mpg (11 percent) over-report. This sort of shenanigan could mean a higher customer satisfaction score from owners who think they're getting better mileage than they actually are. .....
And that got me thinking.. maybe the problem is not voltstats or the algorithm or my analysis. Maybe the car is lying. (I track CS and EV miles separately so did not think to check the overall MPG. )
Sure enough the car is inflating the lifetime MPG; the data on the center council and via iphone and volstat is wrong. The logs show the car has used 25.2 gallons of gas, and the odo says it traveled 2037 miles. So the lifetime should be 2037/25.2= 80.83 But the readout in the car says my lifetime mpg 83.5. If the MPG was really 83.5, it would mean only 24.39 gallons, or a difference of .8 gallons which is well beyond any filling station erros, and Trip A shows more gas used that that! so parts of the car knows its used more gas than its lifetime MPG suggest. I have not found any way to back into the cars MPG computation. Note this computation is not even looking at actual distance vs reported distance (which tires or something might impact). I'm computing based on actual gas vs odo miles.
Maybe its just my volt or my errors. But given Mikes comments that on voltstat.net he is seeing what he though was an initialization error, I'm thinking this is much broader.
So the question is.. does anyone else have enough data to see if this is a broader issue.
Maybe the car is not counting gas used while the car is not moving? I make this hypothesis because I believe the dealer burned gas while it was parked
You might be thinking, why would a dealer run the gas engine for more than a min or two (it starts if you open the hood and its on). I realized I already had suggested this to another dealer. MM can be a faster way to charge the battery for a car that is being demoed, much faster than even a level 2 charger. 15-20 min of MM idle and you have enough CD range to show off the car. I learned about MM that on this list. I was very disappointed when I took my first volt test drive at a local dealer and the volt was in CS mode. When I asked why, the dealer said they had not plugged it in and where they have the charger in the service bay is not a good place to show off the car and somewhat in the way, so if they forget to move it and plug it in at night, they just demo in CS mode. I told them they can always just run in MM mode on the lot and then let people experience EV driving. He asked me to show him, so I switched modes and did about 5-10 min of MM mode during the rest of the demo drive an when we returned to the shop, turn it off then back on it showed 3 bars, enough to for miles of EV demo for the next guy person. I also suggested he setup the phone app to email if they forget to charge (but I guess that still does not work).
So do MM miles while not moving count to lifetime MPG? I someone knows the answers please let us know.
I'm guessing someone that has used it on a cold climate may know from heating pre-start which may be the same. Otherwise, I'll try an experiment when I get a chance on a trip that needs some MM anyhow. At least I can answer if the non-moving gas usage is counted.