When I picked up my Fit the sales guy told me that it was not a good idea to "top off the tank" when filling up with gas. He said that after the pump stopped that is where it should be left. If you were to continue to put more gas in (i.e. round to next dollar), it would trick the computer to think that the car was empty and the ECU would be all screwed up. (I think I saw something in the manual about this too, but can't remember, I take another look).

Is there any validity to this? How are you generally filling up? does it matter to top off the tank?

Perhaps my sales guy was crazy

 

From the manual:

Stop filling the tank after the fuel nozzle automatically clicks off. Do not try to ‘‘top off’’ the tank. Leave some room for the fuel to expand with temperature changes.

Though I bet thats in most every car manual. Personally I do a couple of clicks, I don't care to round to an amount as its on a gas card usually and do not want to overflow gas on the paint.

In warm climates this may be more of an issue coming from a relatively cool storage tank to your fuel tank. Not sure how much gasoline expands with warming.

 

The gasoline wouldn't expand in warmer temperature. It is explained in the forum something about needing to have room for the gas vapor. do a search on it, i know it was talked about before.

 

What about the possibility of it confusing the computer? This is the part that I am most concerned about.

 

Not sure about confusing the computer to think the tank is empty, but too much gas in the tank can screw up the EVAP system.

This is one of those environmental systems that "makes the air better to breath." In the old days, the vapors from the tank simply vented to the atmosphere. Starting in the late 70s/early 80s there was a system placed on vehicles to pull the vapors out of the tank, send them though a charcoal canister, and then into the vacuum system of the car.

Dictionary of Automotive Terms Abbreviations

With the tank overfilled, liquid gas can enter the system and possibly damage some or all of the system. Only designed for vapor - not liquid.

Once click and you should be good. Besides, that extra click today could cost you $.75 or something

 

i really don't think an extra click should mess up the whole ecu. i mean it is a brand new car. usually the pump clicks like that to make sure you don't overflow the tank anyway. if you're close enough to that dollar i say round it off, but if not then just let it go. not worth taking the risk if you're that worried, riiiiight?

 

I always have 'em go to the next dollar, you can't pump your own gas here in the peoples republic and you usually get a few cent discount for cash. That way I don't have a bunch of change rattling around and no problems after 7k miles. At todays prices, rounding up to the next dollar is a quart or so max, probably not enough to overfill after the pump clicks off.

 

Guy doesn't know what he is talking about. There is no way to "screw up the ECU" by overfilling your tank. However like fluffy bunny said it may cause your EVAP system to malfunction. It is NOT a good thing to overfull your tank and there is no reason to do it.

 

There is no reason not to 'round off' the amount to nearest 10c, or dollar if its close, after the pump clicks off. That happens when the level is well down the filler pipe.
There is reason to not fill the tank to the neck as gasoline DOES expand with increasing temerature; the storage tanks below ground are 20 to 30 degees F colder than air temps and certainly your Fit in the middle of the day.
I have filled my tank to the neck several times to get accurate mpg numbers but always drove at least 100 miles afterward so expansion overflow wasn't a consideration. But if you only drive a few miles after filling to the visible neck, you will lose maybe 0.2 gal to expansion overflow.
(But then that's why you should fill-up early in the morning when gas is more dense and you get more than when its hot.) Volume, gallons, doesn't know about density, so a gallon of rocks weighs a lot more than a gallon of air.)
And yes overfilling will likely screw up the evapoative collector system. Its made to handle vapor, not liquid.
cheers.

 

Gasoline station store their fuel in underground tanks. The temperature of these tanks doesn't change with air temperature throughout the day, so any change of density is negligible. The fuel you pump into your car's tank will expand more during the hot part of the day though as it heats up to ambient air temperature. If the station has just recieved a delivery during a hot part of the year (most fuel depots store their fuel in above ground tanks which will be warmer during warmer seasons) the density will be lower as the fuel has yet cool to ground temperature. I never buy gasoline at a station recieving a delivery, not because of fuel temperature, but because impurities (water and solids) on the bottom of the stations tank can be stirred up and pumped into my cars tank.

 

I dont see how topping off confuses the computer. Because the pump isn't connected to the computer. The computer goes by how much gas it sees in the tank, thats it. If you top it off, I dont think the computer cares. Now wether or not its safe, different story. All depends on who you ask and what you believe.

 

I never top off my tank. I don't see the point of rounding up since I pay by credit card. I have a dedicated card for gas purchases and pay that sucker off each month.

 

I have started doing the same thing, paying by credit card. Here in the Fraser Valley it is required that you prepay, credit card just makes sense. And with the high gas prices it is actually working to my advantage because I get 1% back on annual purchases on that card.

 

I get 5% to a certain point, then it goes very very low until the anniversary date, then goes back to 5%. I highly recommend Discover's gas card.

 

Watch out for the hidden fees when using your card. I think ARCO...at least I think its ARCO, charges a small fee if you don't pay with cash.

 

lol, i wouldn't use arco anyway [;

i hardly ever have enough money to actually top off my tank so i don't think i'll be worrying about that. lol

 

Thank goodness there aren't any ARCOs around here, lol. I mainly go to QuikTrip around here. A lot of places like prepayment if you use cash, so the card is more convenient. Plus, you can fill it full (without topping off, of course, lol).

 

i find it amusing how many people actually believe their salesman, yes you can damage the evap system, but not wanting to single anyone out i have worked in the auto service industry for a long time now and virtually all salesmen(women) know very little about the service dept.
they may be well versed in the features of your car but most of them could not find the service dept with both hands and a flashlight.

 

haha, yeah! my salesman said i can take a g35 or a Z easy on a straight from block to block. lol, no business.

 

We have a very small tank & I always do at least a single click sometimes two... & have no worries. I can't believe that our ecu is that delicate!
It sounds to me like the salesman just wanted to sound knowledgeable... & gave you a line of bull.... little did he know that you had a whole forum of freaks to raise the b.s. flag!!