3rd Gen Protege/MazdaSpeed/P5/MP3 General/Maintenance Discussion for 1999-2003.5 Models Only (BJ Chassis)

weird gas mileage

Thread Tools
 
Search this Thread
 
Old November-4th-2002, 10:18 PM
  #1  
Protege Enthusiast
Thread Starter
 
Sbeast702's Avatar
 
Join Date: Aug 2002
Location: Vegas Baby
Posts: 65
Sbeast702 is on a distinguished road
weird gas mileage

I did a little experiment with my gas mileage last time I filled the tank up. I didn't run my air once and saw that I got about 100 miles on the first quarter empty, then about another 100 on the second quarter, now, i'm right above 1/4 tank and I've only gone like 40 miles? Why is that?

I thought I was going to get a 400 mile tank but it doesn't look like it now... was the first half tank just a bad approximate?
Sbeast702 is offline  
Old November-4th-2002, 11:08 PM
  #2  
Master of All Things :{D
 
Sir Nuke's Avatar
 
Join Date: Feb 2002
Location: southeast texas, near houston
Posts: 4,118
Sir Nuke is on a distinguished road
the gauge in any car is a good estimate at best....when I take it easy on the car I get similar results........but my milage is pretty constant regardless.
Sir Nuke is offline  
Old November-5th-2002, 07:15 AM
  #3  
Registered User
 
dewey's Avatar
 
Join Date: Oct 2001
Posts: 246
dewey is on a distinguished road
Gas gauges are pretty inaccurate. Don't base any calculations on them. Some cars are worse than others, but in my experience the needle moves slower when it's near F and faster toward the E.

Fill your tank until the gas pump clicks off. Then perform your test -- drive your test route or for a week or whatever. Then re-fill your tank. The number of gallons (or liters, for our metric friends) you put in is the number of gallons (liters) you burned.

I suppose you could increase the accuracy further by refilling your tank at the same pump at the same station, to remove any variability due to pump sensitivity settings.
dewey is offline  
Old November-5th-2002, 07:23 AM
  #4  
JJB
Protege Owner
 
JJB's Avatar
 
Join Date: Oct 2001
Posts: 731
JJB is on a distinguished road
Re: weird gas mileage

Originally posted by Sbeast702
I didn't run my air once
also, keep in mind that the A/C also comes on (not selectable with the little switch) in the defrost, defrost/floor, and floor positions.
JJB is offline  
Old November-5th-2002, 09:24 AM
  #5  
Protege Newbie
 
YtseProto's Avatar
 
Join Date: Jun 2002
Location: Phoenix, AZ
Posts: 11
YtseProto is on a distinguished road
Talking Lookee...

For even more info on the topic of fuel gagues and why they are sporadic, see this website...

http://www.howstuffworks.com/fuel-gauge.htm

K
YtseProto is offline  
Old November-5th-2002, 11:12 AM
  #6  
Registered User
 
enormiss's Avatar
 
Join Date: Jun 2002
Location: Atco, NJ
Posts: 111
enormiss is on a distinguished road
That's what I was thinking.....

Another possible cause of inaccuracy is the shape of the fuel tanks. Fuel tanks on cars today are made from plastic, molded to fit into very tight spaces on the cars. Often, the tank may be shaped to fit around pieces of the car body or frame. This means that when the float reaches the halfway point on the tank, there may be more or less than half of the fuel left in the tank, depending on its shape.
enormiss is offline  
Old November-5th-2002, 08:22 PM
  #7  
Protege Enthusiast
Thread Starter
 
Sbeast702's Avatar
 
Join Date: Aug 2002
Location: Vegas Baby
Posts: 65
Sbeast702 is on a distinguished road
Cool tips everybody, thanks... the guage in this car is no where near as annoying as my old firebird guage, that thing would go towards E when slowing down and then back towards F when speeding up... very annoying....
Sbeast702 is offline  
Old November-5th-2002, 08:49 PM
  #8  
38
 
Protege5Lava's Avatar
 
Join Date: Sep 2002
Location: Los Angeles, California
Posts: 245
Protege5Lava is on a distinguished road
Possibly the gas tank shape??

This question has crossed my mind many times, I haven't done much testing, but my guess is that the shape of the gas tank is not a perfect cube, as you use more gas from a full tank, the level gets lower and lower, and my guess is that towards the last 1/2 to 3/4 of the bottom of the tank is gets smaller.... just my guess
Protege5Lava is offline  
Old November-6th-2002, 11:37 AM
  #9  
Protege Newbie
 
fuse's Avatar
 
Join Date: Sep 2002
Posts: 6
fuse is on a distinguished road
Re: weird gas mileage

Originally posted by Sbeast702
I did a little experiment with my gas mileage last time I filled the tank up. I didn't run my air once and saw that I got about 100 miles on the first quarter empty, then about another 100 on the second quarter, now, i'm right above 1/4 tank and I've only gone like 40 miles? Why is that?

I thought I was going to get a 400 mile tank but it doesn't look like it now... was the first half tank just a bad approximate?
I believe by law the gas guage has to be accurate at the bottom 1/4 tank and below. The reasoning would seem to be it is more important to have an accurate reading when you are low on gas than when the tank is full.
fuse is offline  
Old November-7th-2002, 10:04 PM
  #10  
ZiO
Protege Enthusiast
 
ZiO's Avatar
 
Join Date: Sep 2002
Location: Edmonton
Posts: 129
ZiO is on a distinguished road
Re: Re: weird gas mileage

Originally posted by JJB

also, keep in mind that the A/C also comes on (not selectable with the little switch) in the defrost, defrost/floor, and floor positions.
Not trying to diss you or anything, but where did you hear this? i cant see it saying this in the manual? i see no reason why it automatically selected.
ZiO is offline  
Old November-8th-2002, 06:30 AM
  #11  
JJB
Protege Owner
 
JJB's Avatar
 
Join Date: Oct 2001
Posts: 731
JJB is on a distinguished road
Re: Re: Re: weird gas mileage

Originally posted by ZiO


Not trying to diss you or anything, but where did you hear this? i cant see it saying this in the manual? i see no reason why it automatically selected.
I read it on this board and was a non-beliver as well... so I went out, popped the hood, and played with the settings. On all the ones I mentioned the A/C clutch was engaged even though the A/C button was "off".

I'm still sore about the whole thing... as I do not like my car thinking for me... but at the moment I am not brave enough to hack up the wiring on the controls to get around it.
JJB is offline  
Old November-8th-2002, 07:59 AM
  #12  
ZiO
Protege Enthusiast
 
ZiO's Avatar
 
Join Date: Sep 2002
Location: Edmonton
Posts: 129
ZiO is on a distinguished road
well that friggin sucks.. but at least now i know i can get more than 650km to a tank then.
ZiO is offline  
Old November-8th-2002, 11:18 PM
  #13  
Certified Sick Individual
 
kc5zom's Avatar
 
Join Date: Mar 2002
Location: Houston, TX.
Posts: 1,141
kc5zom is on a distinguished road
Re: Re: Re: Re: weird gas mileage

Originally posted by JJB

I read it on this board and was a non-beliver as well... so I went out, popped the hood, and played with the settings. On all the ones I mentioned the A/C clutch was engaged even though the A/C button was "off".

I'm still sore about the whole thing... as I do not like my car thinking for me... but at the moment I am not brave enough to hack up the wiring on the controls to get around it.
Ummmmmm. Your car thinks for you all the time.

It's very common because people aren't smart enough to read the manual and actually learn (or remember) how to defog their windows. Refigerated air units are natural dehumidifiers.
kc5zom is offline  
Old November-9th-2002, 08:33 AM
  #14  
ZiO
Protege Enthusiast
 
ZiO's Avatar
 
Join Date: Sep 2002
Location: Edmonton
Posts: 129
ZiO is on a distinguished road
I realize this..... BUT, i have seen in previous cars, IF the AC is automatically selected, the Light WILL be on.
ZiO is offline  
Old November-9th-2002, 10:55 AM
  #15  
Protege Owner
 
protegeDX's Avatar
 
Join Date: Jun 2002
Location: va beach 757
Posts: 492
protegeDX is on a distinguished road
Re: Re: Re: Re: weird gas mileage

Originally posted by Gro Harlem


After hitting that A/C button (with the heat slide all the way on hot), the window defogs, while still pouring in heated air. I have my a/c on all the time year round b/c of this crappy humid climate

is A/C on with the heat slide all the way on hot bad?
protegeDX is offline  


Quick Reply: weird gas mileage



All times are GMT -5. The time now is 09:07 PM.