Does the MPG fluctuates that much after I filled up my gas? why?
Think about it. Just after you fill up you either see "0" because you're burning gas and no moving, or you'll see "99.9" because you started moving witout applying the throttle and possibly on EV alone, thus the high milage. As soon as you pull out onto the highway you're probably going to see 10 then 15 mpg as you give it gas to get that mass moving, then as you get to speed and are say instant averaging 40 mpg the overall tank average will start rising.
The NAV consumption gage can be a little deceptive as it shows consumption per minute not per mile, and since in the US we measure MILES per gallon the bars don't simply balance out. For example you drive 30
mph for 2 minutes averaging 20 mpg and then you drive 60
mph for 2 minutes while achieving 60 mpg. Is the average 40 mpg? Looking at the bars it looks like it would balance out. But actually you covered 1 mile in the 2 minutes at 20 mpg and 2 miles at 60 mpg so you go twice the distance at the 60 mpg level and thus your overall would be 46.67 mpg.
So you're cruising through town at stop lights for 2 miles getting 25 mpg and complaining and then you hit the freeway or better yet a rural road where you can freely practice good hybrid driving. Within two miles of filling up and seeing 25mpg, within 1 minute you've doubled your milage and within 2 minutes you have twice as many miles at high FE as you do at low FE and the number climbs dramatically.
many posters get upset on test drives when what they are doing is driving a "cold" car and seeing the worse driving conditions for FE during that drive. That is pulling out of the dealer lot, probably not taking any chances and pushing it some so as to not hamper traffic (and possibly wreck a car that is not yours). You probably want to goose it at least once to prove you could be happy with it. All in all it's a good test drive but in no way does it really reflect the way you would drive it everyday. Some people are lucky and get to test the new car and take it home and drive it on their commute route. Few got to do that with the TCH.
The less miles on the "new" tank the more variance you'll see because a good mile or a bad mile can overly influence the overall average.
BUT once you have say 300 miles on a tank and you're averaging 40 mpg then what happens when you drive a mile at 20 mpg? Not much. I don't have my calculator but it's probably only a drop in overall of less than 0.1 mpg. I live on a steep hill and I typically lose 0.1 every time I drive up the hill to my house. I seldom gain it all back gliding my cold car down the hill when I leave as my ICE is running warming up the converter and even though I'm going downhill it appears that I'm getting in the 20's for that short time..
Miles per gallon on the trip computer
