just kind of a weird question. i went on a road trip this weekend. ok, the gas tank is 10.9 gallons. (BTW, i have a 92 dx hatch with a jdm d15b vtec) it wasnt quite empty yet but i stopped an filled up, it took 8.2 gallons to fill it up and i went 320 miles on that 8.2 gallons which comes out to 39mpg. but later i let it get all the way to empty, and on empty it was only at 390. which only comes out to 35mpg. so what the hell, does it get shittier because of lower fuel pressure or does the tank get smaller at the bottom? i dont understand what would cause me to lose almost 5mpg at the end of the tank? anyone understand what im talking about?

 

could be your driving style.
My gas mileage would average about 27mpg with it coming out to be 31mpg at times and 25mpg at other times.

 

well this is all freeway driving, no racing or wot at all, very consistent driving for all the miles

 

You almost can not get a consistant number even if we drive the same way. Unless you are on a track with no wind all the time. Weather and incline/decline will effect your MPG. As I track mine off and on for the past two years, I get 30-40MPG.

As long as you are over 30MPG combined, you are fine.

 

When your tank was on empty did you see if the needle went slightly back up? That says the reserve tank kicked in.

 

Yeah, the gas guage is designed so that when it hits empty, you still have a couple gallons left in the tank.

 

reserve tank ?

 

Yes. I think just about all civics have a 11.9 gallon gas tank. When the needle gets to the empty marker only 8-9 gallons have been used. You still have 2-3 gallons left. If you were to keep driving you would see that the needle will move back up slightly. That's when the reserve tank kicks in.

 

I posted the question about 2 weeks ago, and the result was that the dx hatch had a 10.9 gallon tank. and no, the needle never went back up, it went down past the line for the "E."and when i filled it back up it took right at 10 gallons to fill it.

 

errr you have no reserve tank haha

 

ive never heard of having a reserve tank.

 

it varies with your driving style. I still wouldn't complain about 35 mpg that is still good.

 

Do it a few times then come back, You cant base your mpg on one test.
If I did that I'd be getting 11.9mpg to work one day and 17.5mpg the other day.

 

ok, i got some bad info before, the tank in my dx is 11.9 gallons, not 10.9. ok so at almost empty, it took 8.2 gallons to fill it up, and going 320 miles. ok so thats 39mpg. so going 390 on 11.9 gallons is 32.77mpg. thats alot worse, so now what. why does efficiency seem to go down towards the end of the tank?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by a1320honda &raquo;</TD></TR><TR><TD CLASS="quote">ok, i got some bad info before, the tank in my dx is 11.9 gallons, not 10.9. ok so at almost empty, it took 8.2 gallons to fill it up, and going 320 miles. ok so thats 39mpg. so going 390 on 11.9 gallons is 32.77mpg. thats alot worse, so now what. why does efficiency seem to go down towards the end of the tank?</TD></TR></TABLE>


<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by GoLowDrew &raquo;</TD></TR><TR><TD CLASS="quote">You almost can not get a consistant number even if we drive the same way. Unless you are on a track with no wind all the time. Weather and incline/decline will effect your MPG. As I track mine off and on for the past two years, I get 30-40MPG.

As long as you are over 30MPG combined, you are fine.</TD></TR></TABLE>


<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by b16ahybrid &raquo;</TD></TR><TR><TD CLASS="quote">Do it a few times then come back, You cant base your mpg on one test.
If I did that I'd be getting 11.9mpg to work one day and 17.5mpg the other day.</TD></TR></TABLE>

 

this is after three 800 mile round trips, its within 5-8 miles on a tank every time.

 

Are you topping it off or just filling it up till it stops?
Fill up till it stops (who cares how much gas you have before, or how big your tank is). reset your trip odometer and drive. when you fill up again devide the milage by how many gallons you put in.
So if you drive 200 miles and then fill up again with 5 gallons you got 40mpg.

 

im filling it till it flows out of the top. till its completely full. like i said i filled like that before i left, went 320 mile, till there was about a quarter of a tank, filled it up, and it took 8.2 gallons to fill it up. which is 39mpg.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by a1320honda &raquo;</TD></TR><TR><TD CLASS="quote">im filling it till it flows out of the top. till its completely full. like i said i filled like that before i left, went 320 mile, till there was about a quarter of a tank, filled it up, and it took 8.2 gallons to fill it up. which is 39mpg.</TD></TR></TABLE>

Ok smartass do As i said and report back. Most times the pump will stop when the tank is filled to certain level. It's the most accurate ghetto way to calculate mileage. Forget how big your tank is that plays not roll in calculating your mileage.

 

Sounds like you need to replace your fuel filter or get your injectors cleaned. Give Jiffy Lube a holla.

 

Play it safe. Take it to a shop

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by a1320honda &raquo;</TD></TR><TR><TD CLASS="quote">ive never heard of having a reserve tank.</TD></TR></TABLE>

You don't. It's not a motorcycle.

It could very. #1 reason would probably be worse quality gas. The gas at the bottom of the tank may have build-up or particles in it that caused bad gas milage. Maybe the location, traffic, temp, humidity, air quality blah blah blah caused it. Whatever the case may be you would need to do a lot more sophisitcated test to figure it out with equal variables and a better device then your stock fuel gauge etc... Be happy with the milage you get. Most of us would only dream of it.

 

Errr...I have a reserve. Why is that?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by b16ahybrid &raquo;</TD></TR><TR><TD CLASS="quote">

Ok smartass do As i said and report back. Most times the pump will stop when the tank is filled to certain level. It's the most accurate ghetto way to calculate mileage. Forget how big your tank is that plays not roll in calculating your mileage.
</TD></TR></TABLE>

ok, i didnt say when the pump stops, i said when gas flows out of the top ot the filler. if your going to be a smart ***, be sure you know what your saying first.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by a1320honda &raquo;</TD></TR><TR><TD CLASS="quote">ok, i didnt say when the pump stops, i said when gas flows out of the top ot the filler. if your going to be a smart ***, be sure you know what your saying first. </TD></TR></TABLE>

Ok for one I thought you were being a smartass by saying that you fill it up till the gas flows out the filler. I didn't think that you were serious.
I know what I'm saying do you?I mentioned the pump stopping at a certain point for a reason, it's consistant.
When you fill up, the pump will generally stop at the same point so fill up that way so you get a consistant amount each fill up (when testing).
Next, your tank size doesn't matter one bit when calculating mpg. Sure if you flled it up completely then drained it completely it would be needed to calculate the amount of fuel used. Since your not doing that tank size doesn't matter. Plus you know exactly how much fuel is going into the tank when you refill.
Simple as that.
Fill up, drive, refill. Then take the amount you had to replace in the tank (say 5 gallons) and devide by the miles driven (say 200) = mpg
5/200= 40
Is this clear? Do I still not know what I'm saying?