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I was a little disappointed with 32mpg on my last fill-up (down from 34 on the prior two tanks). I'm thinking the loss was mostly due to trying out alternate commute routes, and being less familiar with the traffic patterns and stoplight timings. Daylight saving time may also have played a role, if only because I was FASing less (and leaving the headlights on when I did it).

I'm always wary of the gallon level that the pump tells me. Most of the time, I set the nozzle to the lowest-flow notch, wait for the auto-shutoff, then "top it off" to squeeze another 1/4 to 1/2 gallon in. Of course this is to the detriment of my mpg result, but I figure it gives a more accurate reading, and helps negate variations in pump auto-shutoff behavior. My wife's CR-V tends to spill out when topping off, but ol' Giles has never overflowed.

Should I just trust the pump auto-shutoff and take the higher mpg? Is "topping off" a bad idea?

brim to brim is the only for sure way .....

The automatic shutoff is there for a reason, and it is against the law in most locales to fill beyond it. It keeps the majority of raw fuel vapors - which are toxic - from escaping into your local atmosphere.

Please stop filling beyond that point unless you have a Prius, in which case the fuel bladder sometimes need some coaxing at fill time.

Hi Brian:

___Unless there is a vapor recovery nozzle, there is no vapor recovery HW in the way in the filler neck to pull vapors in from a top off that I know of. I have never read that it was illegal in most places either.

___Good Luck

___Wayne

At least fill up with the same nozzle each time.
Some seem to be more sensitive than others.
Just a few tenths of gallon can skew your MPG numbers

I'd top off to a point. The Initial auto shut-off tends to be unreliable and is tripped by normal fueling turbulence. "topping-off" at the same flow rate until the second cut-off is OK. trying to "top-off" to the very brim by pulling the nozzle partially out is risky.

Thanks to everyone for the replies!

I think my main concern would be spillage. On consideration, I think I'll avoid topping off from now on, just because there's the potential of wasting gas. Will be nice to see that extra 1-2mpg once in a while too (though it shouldn't affect the overall average).