Instead of going 200 miles before you have to fill up again, you can now go 203 miles?
I see people at the gas pumps all the time, click click, click click, trying to get that last ounce of gas into their tank.
What the heck are they doing???
When I was a kid, my mom would always do it. She was trying to get the total price to be an even dollar amount, which was easier to pay. (This was prior to all gas stations requiring prepayment.)
Stupidity I guess. When I last had a car and gas was hovering around $4/gallon I would certainly wring out those last few drops after the pump automatically stopped but I would never keep pulling the trigger. It stops because it’s *supposed *to stop!
Are you sure that’s what they’re doing?
I’ve seen people “prepay” with debit or credit and then do something similar trying to meter out the exact amount that they’ve pre-authorized for. (I guessing they think that they’ll be charged the amount that they’ve keyed in regardless of what they actually take.)
I want to maximize the time / distance between fill-ups. I won’t fill it to overflowing, but if the pump is one where it’s moving really quick (and therefore kicks off fast because of the gusher of a back flow), then I’ll make sure it’s really full. And I mean full, damn it!
Some pumps have a hair trigger “stop,” and will kick off when I know damn well it’s not full. I just want to make sure the tank is really full, given how astronomically important my time is. (To me, anyway.) But It’s usually just one or two more squeezes, not several, if that makes a difference.
I always have mine go to a specified amount, ending in the same cents every single time. For example, $8.12, $42.12, etc. That way if anyone ever swipes my card to buy gus, I’ll know which charges are fraudulent if they don’t end in .12.
Around here, at least, when I prepay for $20 worth of gas, when the meter hits somewhere around $19.75, the rate of flow will slow down significantly, and if I am holding the pump bar at full speed ahead, it will quit working. It’s like I have to click that bar for every penny’s worth that I want pumped.
Calling a common human quirk “stupidity” is a little harsh. How many odd things do we do without totally reasoning them out?
Anyway, one good reason to top off the tank is to have an accurate measurement of fuel consumed. Since each pump is different, the only way to be sure you know how many gallons were really consumed is to top off the tank each time. Then, if you reset the trip odometer each time, you can calculate your fuel efficiency more accurately
These days, many cars show current and cumulative MPG on the dash computer, so the need to calculate one’s own mileage is fading.
My Dad puts his foot on the bumper and bounces the car up/down a couple times. Gets an extra pint of gas that way. 
Why ?? <shrug> It makes him happy.
My last car ALWAYS cut out too soon, and if I “topped off” I could put another half gallon in it. My current car does not do this, and after six months or so I broke the habit.
A few extra miles or a slightly more precise mileage calculation (probably less than 1% difference) strike me as minimal and nebulous benefits – how often does that extra three miles of range really make a difference in how often you need to stop for gas?
Avoiding the possibility of screwing up part of the evaporative emission control system by pushing liquid into a device designed only to deal with vapors strikes me as a worthwhile benefit (could cost hundreds to evaluate and repair).
Do what you want, but I’d say the reasons to top up are weak and contrived. If you do mess up your EVAP system, I or one of my colleagues will thank you for the business. 
I thought it was bad to do this. My car will sometimes shut the pump off when I’m filling the tank, and after research I found out that it could be due to the former owner of my car topping off the tank. The evap canister get saturated, and that can cause the pump to shut off while filling. So, in a way it is stupid to top off.
My car’s computer is pretty inaccurate. I get much more accurate results calculating my MPG with a spreadsheet. I don’t need to top off to do this.
When fueling my Jeep, I can get another 1/2 to one gallon of fuel into the tank after the nozzle clicks off. That’s an extra 10-20 miles on a tank, which means that I can refuel at my preferred station instead of somewhere else. (And yes, I can get more than 20 mpg in the Jeep by driving it carefully.)
I do not top off the Prius. The owner’s manual says not to. Also, I try to fill up at the same pump at the same time when I refuel. I’ve been keeping a mileage spreadsheet since I bought the car from a friend in 2008. Granted, the nozzle doesn’t click off at exactly the same time each time, but I reckon it’s less of a variable than using different pumps at different stations. (I’m averaging 47.3 mpg. The average increases in Summer and decreases in Winter.)
I don’t really keep “clicking” the pump to get every last drop I can possibly squeeze in, but I do top it off because it’s frickin’ COLD outside. So, I think if it’ll be even another day’s worth of fuel, I can (overall) reduce the number of times I’m at the pump during winter.
At least that’s what I tell myself.
I keep the tank above half full for a few reasons.
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Gas weighs a little over 6# so an extra 10 gallons gives me 60# extra of weight over the wheels of my truck to help with traction on winter roads.
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A full tank should theoretically accumulate less condensation that can rust the fuel lines and potentially cause starting problems. My tank is plastic so that’s less of a problem. All the fuel is at least 10% alcohol so that pretty much takes care of gas line freezing.
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If you run a tank empty, expect to be buying an expensive in-tank fuel pump in the coming months because the pump will be damaged by running dry. The pump requires fuel to pass through to keep it cool. Even if you don’t run your tank empty, having a full tank helps the fuel pump work more easily.
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With unstable conditions around the world, it gives me a warm fuzzy feeling to know I have my own 35 gallons of fuel on board and won’t have to wait in some line paying emergency pricing.
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Winter weather is unpredictable. I went out for a walk with dry pavement and now there is a fresh inch on the ground on my return. I hate fueling up in bad weather and also adding extra water to the mix while gassing up. (See #3 above.)
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This is a long shot. We have a few expressways here that are below grade with 20’ walls on each side. I like to think I could live down there in my truck and keep warm for one hell of a long time if needed.
I don’t go nuts over this issue. When my tank is half empty, I fill it the next available dry day. And if I am driving a long distance, I’m not afraid to run the tank down to 1/4 or 1/8 if stations are available.
I ask that my tank doesn’t get topped off. If the gasoline spills, it ruins the paint.
Sometimes I wonder what would happen if I were in a high speed car chase with a madman and that three extra miles made the difference between life or death. Other times, I think about it as a trip to the emergency room where seconds count or running out of gas in the middle of nowhere during a blizzard. People may scoff but all it takes is one time for it to be completely worth squeezing in those last few drops of gas.
‘The three most useless things to a pilot are the runway behind him, the altitude above him, and the fuel that’s still in the truck.’
The nozzle shuts off because of a vapor sensor in the tip. However, the gas dispensed is measured at the pump. Therefore, some of the gas you’ve paid for is still in the nozzle and hose.
If you click after the pump stops you get a little bit of that overcharge.
Don’t worry about it though, it evens out. You get that little extra from the previous user, and your extra goes to the next person.
Good point. Never over fill the tank. Cut the pump at the first stop-rounded to even change. You can flood the emission system and cause temporary running problems and some longer lasting emission device problems.