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Hi all--

Apologies if this has been covered elsewhere, I looked a little, I promise...

Last week I filled up my 2007 HCHII for the sixth time. In all previous fill-ups, my hand-calculated FE was about 1.0-2.5 mpg higher than that indicated by Trip B, which I use to record the tank. The magnitude of the error varied, but it consistently came in lower than calculated values. Then, on tank 6, suddenly Trip B got it dead-on. Any explanation for this weirdness?

For the other variables, things are pretty much the same -- I fill up only to the first click at the same gas station (and frequently the same pump). I fuel up soon after the amber light comes on, and I typically get about 10.1 (+/- 0.1) gallons in. I'm fairly certain the G part of MPG is therefore controlled.

I will say Tank 6 was my highest FE to date and I squeezed out just over 500 miles. Is the FE calculation in on the trip odometer subject to errors that are somehow minimized over longer distances? Does the fuel type or temperature play a role (it has also been warmer of late)? All very confusing. --RN

No one sneaked in and installed a Prius bladder for you, did they?:)

Seriously, when I see weirdness in fillups and MPG calculations, both mine and in those reported on the Prius forums, I curse the bladder. Nice idea, but I'll take a conventional tank. Wanna trade??

Jimbo--

My wife has an 06 Prius, and since September when we got it neither of us has been able to get more than 8-9 gallons into it, and that's after the gauge flashes at her.

More on my problem--

I've seen people complain about the 1.0-2.5 MPG discrepancy and also the odo discrepancy, but that still shouldn't explain why suddenly it's correct. And I realize one point does not a line make, so I'm sure I'm prematurely interested, but I thought it curious. --RN

I saw this kind of thing even in the Accord, which had a normal tank like your HCH. Even without the funky bladder you can still get several percent worth of variability from tank to tank. Odds are it will make up for itself on the next tank.

HCHCIN -- I've often see a discrepancy, usually with the trip-B being lower than the calculated mpg. Looking at my data, only a couple times in my last 10 tanks have they agreed within 0.1 mpg.

I use the trip-B as a guide for what to expect but don't take it real serious....just an approximate. I'm always happy when it's understated and my real (calculated) mpg comes out higher.