Consider this if you will. The Australians have HCH's as well - and as we all know they are upside down and will use the top half of the tank first. So my question was well meant.

To be serious, the second half should give slightly better fuel economy as there has been a reduction in weight of some 6 gallons-weight.

I haven't noticed any fluctuations in mileage with the start or end of a tank - mine usually stays quite consistent given identical driving conditions - but I have noticed that the last 1/3 or so of the gas meter will disappear much more quickly than the first 2/3. Usually when the fuel gauge is reading 1/2 or so, I've already got 450 miles or so on a tank, and none of my tanks ever reach 900. That said, I'll reiterate that the FCD shows no change in MPG during that last 1/3.

I've been thinking about this for a bit, and I guess the only thing I can post is speculations... So, please don't get offended thinking that I'm assuming anything about you or anyone else. I'm just speculating!

My average for the first two years that I owned my car was about 43 or 44. I remember being super frustrated the first little while when the best I could get was 42.7 per tank. I hadn't found GH to get tips from yet! Eventually I just sat back and enjoyed the ride, got to know my car, got to know what made it more effiecient and what didn't.

Lately (after 2+ years driving it) I've been getting 46 mpg, and this tank 48.8 Started going up when I made sure my tires were pumped properly and a bit higher than usual. I also don't drive over 72 miles per hour-- that seems to be the point when the FE drops faster. I've been practicing the tips.

Anyway, my first speculation is that maybe you're like me. It takes time to "break in" the car, or maybe it's to "break in" you as a driver. Even after reading all the tips on this forum it take practice to do them right.

The other thing is, I definately notice that I get higher MPG on the first part of my tank, and that sometimes it falls as it goes. For the first 50 miles or so it does the usual fluctation of low and high as the averages play out. I think it still does that as we go, but is less noticable. I don't have any guess as to why, except that it's harder to budge the real average the more miles you go... and the more miles you go the more it's closer to true...

This doesn't explain anything about getting 42 mpg after resetting for the last 300 miles of a tank. Sometimes, despite everything, the average on a tank sucks.

Here's another speculation. Maybe you need to switch gas stations. Or consistantly go to just one. I have recently been going to one more than I used to, and going less to another. Sometimes I notice that if I fill up elsewhere the average changes. "They" say that all the gas comes from the same place. Maybe so, but petrol from some stations ends up with worse FE than others!

Ok, anyway, enough of my rambling. Major points: You're not alone. Relax, enjoy the car--you're doing better than most cars on the road anyway!
--A