When to fill up the tank
 

I apologize if this has already been covered in another thread. However, my question is: Is it better to fill up the gas tank when it's near empty, or when it's half empty? There is less weight, therefore some better mileage can be gained when the tank is near empty, however I have also read that with a small amount of gas in the tank, a lot can evaporate. What are your opinions on this?

Always better to have less fuel in the tank for less weight.

If you always go to the same gas station and same gas pump the same time of day and drive the same route at the same speed you will eventually be able to find out the absolute maximum number of miles you can drive before you must get gas.

Works pretty good most of the time. But with E10, you might get an unpleasant surprise once in a while. Then you're EOC for real LOL!!!!!!

The downside of running on empty all the time is excess heat in your fuel pump resulting in premature failure. Modern in-tank fuel pumps depend on being totally submerged to dissipate heat.

Being the poster child for running my tank almost completely empty before filling up, I have to disagree. I bought a Civic VX brand new in 1995, always ran it close to empty before refilling (i.e. the pump usually stopped at 9.5 - 9.8 gallons for the 10 gallon tank), and I never had any problems with the fuel pump in the 225,000 miles I drove the car. I also used to overfill it with 3 - 5 gallons extra, after the pump stopped. I could trickle it in slowly. Believe it or not, I never actually ran out of gas...came close 2 times, but always made it to the gas station.

At times, I've put 11 gallons into my gas tank. How many gallons have you put it in one fill up?

I can counter your data point with a fuel pump that died at 120,000 miles. Perhaps a 1995 VX fuel pump isn't very sensitive to heat...

yup, ive heard of this happening in the s-series GM trucks and blazers

whoppign $300 to replace soo id rather not risk it:p

You're also best off to fill up in the morning. I see about a 3% difference - so much so that it's been YEARS since I did a regular fill in the daylight hours. Usually fill up between 6 and 8 am. Many years in the desert taught me this one.

summer's coming and it gets to the 80's and 90's here, should i fill up with 1/4 a tank with my 94 civic?

Here in Canada the pumps are temperature compensated, so there wouldn't be much, if any, difference.

That is one distinct advantage that Canada has over the US, another being that Canada is required to post price increases a week or two in advance. (At least British Columbia, last I heard) Implementing these two things would seriously help the US and stabilize gas prices.

Speaking of overfilling the tank..

I remember on the old "Candid Camera" show they took a VW beetle and connected a huge tank to the fuel filler. This was back in the days when your gas was pumped for you and VeeDubs were the smallest thing on the road.

Anyhoo, they pulled into a station, told the pump jockey to fill it up and then went around to the bathroom. The pump just kept going and going, the pump jockey started to freak at about 25 gallons or so and by the time it got to 30 he was looking under the car.. Funnier than all get out..

The candid camera show I will never forget was the one (black and white) where they had Dolly Parton pretending she had a leg injury and she would ask men to carry her into a store.

regards
gary

It's amazing what an attractive woman can get men to do, eh? :D

This is data from my daily commute over the last year+. 560 entries.
125% is filled above the full mark on the gauge.
My car has a bad stumble when it's really low, so don't put too much stock in that reading.

Attachment 1282

Q1 and Q3 are the 25th percentile and 75th percentile. Think of it as halfway between average and max or min.

Here in Nova Scotia we don't know that much ahead of time what the price increase will be. Each week the price changes, you can usually hear on the radio the day before whether it will go up or down. And usually an estimate of how much. But other than that, you just have to wait and see.

Having replaced high mileage fuel pumps in both my vans recently, I can say that GM did do something right with the design. Both have the actual pump in a little cup that fills with fuel and stays filled when the tank is low to keep the pump cool.

For my good van I bought a Delphi unit from GetGMParts.com $260 + $15 shipping. For Grumpy I bought a fuel pump assembly rebuild kit for $30 on eBay, little bit more work but Grumpy runs for now.

If your vehicle has a fuel filter be sure to include it in your maintenance schedule, definitely helps to extend the life of the pump.

jad: "Then you're EOC for real"

That's funny!

I did actually run out of gas once, on purpose, because I really wanted to know my true capacity (and even though I've heard lots of reasons why it's considered a bad idea). And I managed to be heading downhill toward a gas station at the time (although I also had a gas can in the car), and literally coasted to the pump in EOC mode. Just like you said.
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cems: "the pump usually stopped at 9.5 - 9.8 gallons for the 10 gallon tank"

Wow, you really were running close to empty. When I did my dry-tank experiment, the pump stopped when it reached 10.138. Of course, even when you had only 0.3 gallons left, that was still worth about 15 miles, since it was a VX.

"I also used to overfill it with 3 - 5 gallons extra"

You must mean 0.3-0.5.

I once did some very stupid overfilling, and realized (too late) that I was paying for fuel that was being vacuumed into the pump's vapor recovery system. Those little holes at the end of the nozzle carry a vacuum. Now I'm done as soon as the pump stops.
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1993: "At times, I've put 11 gallons into my gas tank"

I've seen confusing information about how big the VX tank is. Some references indicate that all VXs have a 10 gallon tank. Some other references indicate that it was 10 in certain years, and 12 in other years.

Maybe you have a 12 gallon tank. If you have a 10 gallon tank, and paid for 11 gallons, I'm pretty sure you were sending gas into the pump's vapor recovery system. I learned the hard way.

I once looked at all the VX gaslogs, looking for very large fills. I found only a very small number of fills over 10 gallons. The record (at least as far as what I could find) is 11.174, here: https://www.gassavers.org/garage/viewgaslog/796. I think the only other car with a fill over ten (10.236) is here: https://www.gassavers.org/garage/viewgaslog/217.

Those cars are a '92 and a '93. I think somewhere along the way I got the idea that those years had a 12 gallon tank, and then they switched to 10. Not sure, though. But I'm darn sure that my tank ('95) is 10, not 12.
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fume: "by the time it got to 30 he was looking under the car"

When I did my stupid experiment involving overfilling, I did literally look under the car, because I was surprised at the fact that it seemed I could keep squeezing more and more gas into the tank. I really thought I might be forcing it out onto the ground, somehow. It was only later that it dawned on me about what those little holes at the tip of the nozzle were doing.

I knew that pumps have some kind of vapor recovery system, but I didn't realize how subtle and effective it is. It's different from a few years ago, when the nozzle had that large bellows over it. Those were easier to defeat, if you were determined to fill to the very tippy-top.

What do "Q1" and "Q3" refer to?

I don't know specifically as per mpg concerns but what I do know is I don't play the stupid fuel gauge game anymore lol... 1/4 tank and it's high time, fill'er up and now, never do I let my cars fall below 1/4, it just ain't worth running out of gas someplace.

Better off letting the car sit for all that, just don't drive.

Q1 and Q3 are the 25th percentile and 75th percentile. Think of it as halfway between average and max or min.

edited the post above with the same.