Accurate fuel fill without topping off?

[sbergman27]

Originally Posted by docB

Filling to the very top is nice if you have all the time in the world. Plus you are hauling the weight of that extra fuel.

Well... That extra 1.1 gallons of fuel gets me an extra hour (or so) down the road before the next refill. So on a "time economy" basis that doesn't make sense. However, on a time spent out in the cold and whistling wind" basis it might, since a fuel stop involves substantially more time than just the pumping time. (Exit, find the station, find a pump... etc. etc. ... update the scangauge, get back to the highway, get back up to speed...) But the time spent out in the cold is significantly increased. And I really, really don't like the cold.

Gasoline weighs about 6.5lbs/gal. So 1.1 gallons weighs about 7lbs. Or about 0.25% of the weight of the car (with me and my suitcase in it). Of course, the *average* added weight over the course of the tank is half that, or about 0.125% of the weight of the car. And on the Interstate, wind resistance dominates. The difference made by the extra weight works out to about 0.02 mpg.

However, despite the humorous flights of fancy in the public service announcement, there are enough rational reasons not to top off that I've switch to filling at the pump's slowest setting and then pumping as much as I can by pulling the trigger *ever so slightly*, just once to make sure that the automatic mechanism got it right the first time. It doesn't work out to more than 0.1 gallons more. And the method seems to give me a consistent adjustment factor on the scangauge.

-Steve

[STC]

I fill up at the slowest pump speed. Once the pump clicks and shuts off, I wait about 10-20 seconds and fill around .100 of a gallon more.

By filling up at the slowest speed reduces the gasoline vapors, therefore not wasting the gas that has evaporated.

This is less volume in a fill-up... saves a tiny bit!

[bkrownd]

I've always done one shot past the first shut-off just to make sure it wasn't cutting off prematurely - occasionally pumps will shut off a bit prematurely. It's absolutely restrained compared to how my relatives pump gas. ;)

We don't have the vapor sucking pump nozzle in Hawai'i. Mmmmm...those lovely heady gas vapors. :D

[Ilovemyyaris]

Originally Posted by Yaris Hilton

It'll still clog up your charcoal canister.

How many times till that happens? Is that just a long term effect?

I've been topping off all the way to the top of the tube to make sure my mpg calculations were as accurate as possible. I haven't noticed any bad side effects. I just thought it wasn't a good idea because of the risks of spilling gas when it gets close to the top. I wont be doing that anymore.

[Idahotom]

I just use the same pump at the same station every time (locally of course) and just quit when it clicks off. I'll even wait for that pump to be available, and I park the exact same way and spot, that should be consistant enough. I use the fast pump mode, I just like getting in and out of the station quickly, while other drivers are still pumping (and paying).!

[TLyttle]

Yeah, why is that so hard to understand? If it was a good idea to clog that cannister, they really wouldn't install it in the first place! It is a SYSTEM, dammit!

[The Limo]

If you are really interested in your mileage then join a site such as fuelly.com or spritmonitor.de (European site). These sites keep track of your MPG plus other expenses. I find after about 10 fillups that your MPG stays about the same.
Roy

[Em_]

topping off is very bad on the charcoal canister

i topped off my my 2005 echo a couple of times and i had to endure the check engine light 5 months p0446 i think

i erased it regularly and finally after 5 months it didn't come back it' like some gas went somewhere where it wasn't supposed to and it took a while to evaporate