Are you sure this is not due to the lesser weight of less fuel on board? Perhaps you never noticed it before. I seem to get at least several mpg less upon filling the tank, and mpg gradually increases as the tank is consumed. This seems to repeat with every tank. Maybe I will go on a starvation diet and after a few months see how much my mpg has increased :blink:
You introduced several variables at once, but my guess would be that the wind swung around in your favor on the return trip. You pretty much went northwest and then returned toward the southeast, right? Prevailing westerlies could easily do that. There's also a certain amount of break-in of the *driver* that happens, and while you were on cruise much of the way sometimes how you handle the little routing bits at either end counts for a lot. I've seen MPG averages stay rock-steady for six hours on an interstate, and then the nice little warp-stealth glide into a rest stop pops it up a point or three. . _H*
As a suggestion, make a log on your next cross country with each segment recording, start/stop miles, temperature, fuel (if you top off), speed, wind direction and speed, altitude of start/stop locations and any other notes that might apply. Then for grins, try different speed increments for the segments, 65, 70, 75, if possible. One other thing, there is a scanner that works very nicely with your model and I think it can record the OBD data. I don't have any experience with it but it could give more insights. GOOD LUCK! Bob Wilson
<div class='quotetop'>QUOTE(catgic @ Sep 6 2007, 04:21 PM) [snapback]508152[/snapback]</div> Catgic... My apologies, I didn't read your post carefully enough... thought you made both directions on 1 tank. Actually I HAVE noticed a "Surge" after I hit 5000... being the eternally curious person I am, I was thinking of many possible reasons. The problem is that my Prius goes over 2 weeks between fillups and a lot of changes can happen during that time... I changed my oil to 5w30 (do not know what the factory puts in), pumped tires to 40/38 (do not know what the dealer put in), got my EBH and started using it on the higher tank, had a BGT episode (barfing gas tank) on the higher mpg tank, the weather cooled off a little so less AC use, getting more experience driving this fantastic car, etc. I was thinking it was a combination of all of the above that gave me 66.6 mpg (pump based) on that tank, when my highest previous was 57. There are so many variables involved, I still doubt there is something that "breaks in" at around 5k miles. Just my $.02, but glad we are both getting such great numbers all of a sudden! Oh... I'm still eating the same. And I have all of them except DS9.
Since everyone seems to hit it at 5000 miles, could it be that the computer expands the SoC range of the battery to the full range where it might be something less during break in?
I know very little about cars and production but is it possible that Toyota (and maybe others) use a special grade of oil in a brand new engine since they can only assume the car will be spending part of the beginning of its life not being driven while on a ship or on a lot? I read a few posts stating the original oil was filthy and sludgy by 5000 miles and a subsequent 5000 miles didn't make the following batch nearly as dirty... I have yet to hit my 5000 but I will report back when that comes around...
You can get a 2-to-3 mpg difference due to elevations along your route. I've seen that going from my house to a destination that is lower in elevation. High mileage outbound, lower by 2 or 3 mpg coming home. Harry
