Varience between tanks?
 

Well was finaly time to refuel. i use the low fuel light as a guide to refuel and i had thought i was on a decent tank (35-36mpg) was just over 300 miles and as im pumping i'm figuring maybe 8.5 gallons would be a good point but it hit there and was still moving after 9! finaly stopped at 9.3X and i clicked it once and then shutoff. worked out to 31.9 mpg! :(

this is my worst tank ever. I had started doing engine off coasting and figured that anything over 300 miles for lil silver would be a good tank but i got proved wrong. SG was showing just over 30 for the tank but i had been thinking it was off cause last tank was over 36 and that quite a drop from one tank to another,


works out to 11% drop. probly the weather and my short trips combined. i have been using a new route to work and it keep my speeds down and a few opportunities to coast but i guess my car like the steady pace better. or maybe pump was off?? oh well now that i have been logging will just hope was a 1 time thing.

Worship at the altar of the god Average. Post faithfully and he will level the mountains and fill the pot-holes, as well as make some sense of the occasional random superlative or abysmal single tank readings.
Check out the tank-by-tank numbers in my garage. Your 32 out of an expected 36 isn't that far out in comparison.

if your average fill is 10 gallons and if there can be an error of up to 1.5 gallons thats an error margin of +/-15%

Yep, law of averages owns you. Look at my gaslog - very hilly, but I post EVERY tank and it all evens out.

As you can appreciate, other people have the same problem you explained, more or less. I get bamboozeled by this more regularly than not. I think it might be more noticable because your mileage is higher, so that any variation shows up more. Also, I think this stuff is a lot like trying to watch a pot boil water, it just won't boil while you watch.

Post all of your tanks to the gaslog and keep working on it. The gas log has been a great source of insight for the very reasons you have just experienced. You are not alone!

I think the 36 might have been a fluke tank. the refill before the pump had stopped and i probly click 2-3 time to get to the next dollar ammount then the next fill i click once and that probly made it look like i used less. i'm gonna have to use same refill procedure now to keep that variable somewhat level. warmer weather is coming and i know i will be able to hit tanks of 35+ and hopefully pull a 40.

You should figure out the gas tank capacity since a low fuel light indicates about 2 gallons remaining you mayhave been short pumped or temperature corrected for colder gas (yeah right). My SG has been within about .1 gallons every time but I keep clicking until it spills on the ground or darn close to it - I usually just pump for a couple of seconds and let go and wait a few and then repeat about 5 or 6 times so that it never reaches the vacuum holes on the filler nozzle. It seems to work out pretty good that way - still think a clear sight hose with an over flow tank would be ideal.

i found the biggest variance between tanks has to do with the angle of the ground. if the driver's side rear is up it fills more than if the driver's side rear is lowest. the difference is rediculous.

If anybody ever feels bad about the variance between tanks, just have a look at the Warp Wagon's gaslog and feel bad no more. Today was the first time in two months (on the nose, actually) that I've been able to get a calculated average to come reasonably close to the MFD's estimate. Before now they have been flopping back and for between high 30s/low 40s and mid 50s while the MFD tells me something in the range of 47-48mpg.

The Prius is a strange beast, indeed. Strange but good. ;)