Terrible Gas Mileage

20SilverGT00 · 03-05-2007, 07:30 AM

My '00 GT's mileage has steadily fallen off for the last 6 months. I was getting roughly 22-24 mpg around town for forever, but then it started falling. I didn't think my driving habits had changed in particular, but to prove my point to myself, I drove very conservatively for the last tank and got 16.5 mpg. What happened? I replaced plugs and wires around 30k ago. I really don't think it can need that again. I've run Techron injector and system cleaner, every 3000 miles since new. The only thing I can think is maybe something wrong with the MAF. The only mod it has is a Dr Speed Stage 3 CAI. I would appreciate any advice as far as where to look.

bballr4567 · 03-05-2007, 07:32 AM

When was the last time the fuel filter was changed??? I changed mine when I started to get some bad MPG on tanks and I got back the mileage I lost.

Also run a few bottle of fuel system and injector cleaner through the system. You prolly have over 100k miles and it might help too.

20SilverGT00 · 03-05-2007, 07:35 AM

Yeah, I have 130k on it. I have run techron injector and system cleaner on a regular basis, however, the fuel filter hasn't been changed in quite a while. I'll definitely do that. Thanks for the advice!

bballr4567 · 03-05-2007, 07:45 AM

If you tackle this the easiest way to change it is to PUSH the green clip all the way up on the side that is closest to the rear of the car. I would of taken pics of it but I was covered in gas so I just wanted to finish. Forget about the correct technique. Just be careful not to break the clip.

20SilverGT00 · 03-05-2007, 08:38 AM

My car is a 2000 and I believe it has a different clip on the filter, does anyone have any advice on removing the clip?

gectek · 03-05-2007, 02:54 PM

they are all the same, and what you do is take a really good look at it, one piece of the tab will show a part between it, so then take a knife or screwdriver and put it in there and pry the tab out, then push it backward and that will release the fit it has on the filter

slickjoe · 03-11-2007, 12:37 PM

I get bad gas mileage, but that's because I drive fast

.

Panacea · 03-11-2007, 08:53 PM

You have noticed that it's winter out, right? I avereaged 17 to 19 mpg (more towards 17mpg) in the winter time in my 99 GT. Wait till summer and then see what your mileage is.

cardude007617 · 03-11-2007, 08:55 PM

ya winter does affect the mileage u get, id do that too^^

gectek · 03-11-2007, 08:56 PM

dont forget rain also

aaronandchris · 03-14-2007, 07:54 PM

If you have replaced the fuel filter and still get bad gas mileage you may want to look at the fuel pressure regulator. My gas mileage started to get worse and worse and I had almost perfect car maintenance. I replaced the fuel pressure regulator and my gas mileage improved dramatically.

20SilverGT00 · 03-15-2007, 02:07 PM

What should the fuel pressure be when the engine is idling?

Mirage85 · 03-15-2007, 02:09 PM

I havent seen this mentioned, but hows the air filter? Perhaps try putting the stock filter back on and see if your mileage goes back up?

20SilverGT00 · 03-15-2007, 02:39 PM

I have put my stock intake and filter back on, mileage is still poor. I also cleaned the MAF and the throttle body.

Sprucegagt · 03-15-2007, 07:01 PM

Quote:

Originally Posted by 20SilverGT00

What should the fuel pressure be when the engine is idling?

At idle with the vaccum line off the fuel pressure regulator you should have 51 - 55 PSI of fuel pressure

WeibSunder · 03-15-2007, 07:24 PM

This might sound totally retarded, but my dad was having the same problem with his little S-10 2.2 4 cylinder, and someone told him to change his thermostat and he did and POOF, his MPG went from 12 mpg back to the 25 that he use to get. You could always try that, worth a shot.

gectek · 03-15-2007, 07:46 PM

well rule of thumb is that if you are running a colder t stat then you will lose a little MPG, due to it richening up the regualr mixture

drumking1721 · 03-24-2007, 08:30 AM

yea so i changed my fuel filter yesterday....i was 93 octane or higher...and yea when took off the old one and dumped out the gas...it was coming out black...so i think i found my bad MPG problem haha

Mike Jung · 03-24-2007, 10:06 AM

Quote:

Originally Posted by drumking1721

yea so i changed my fuel filter yesterday....i was 93 octane or higher...and yea when took off the old one and dumped out the gas...it was coming out black...so i think i found my bad MPG problem haha

^
You are lucky you didn't have mis-fires, from lack of fuel flow

Mike Jung · 03-24-2007, 10:11 AM

Quote:

Originally Posted by WeibSunder

This might sound totally retarded, but my dad was having the same problem with his little S-10 2.2 4 cylinder, and someone told him to change his thermostat and he did and POOF, his MPG went from 12 mpg back to the 25 that he use to get. You could always try that, worth a shot.

^
Might of been a stuck open/failing thermostat.

If the engine does not get up to normal operating temps.
& runs cold.
It will run richer until it does.

With a stuck open thermostat:
The engine coolant goes to the rad to early (by not being closed) & cools the engine coolant down before it gets to the normal operating temps.
So it would take forever to get warmed-up to the normal operating temps.

03-05-2007, 07:30 AM	#1
20SilverGT00 V6 Enthusiast Join Date: May 2005 Location: Winthrop Harbor, IL Age: 36 Posts: 26 Vehicle: 2000 Grand Am GT	Terrible Gas Mileage My '00 GT's mileage has steadily fallen off for the last 6 months. I was getting roughly 22-24 mpg around town for forever, but then it started falling. I didn't think my driving habits had changed in particular, but to prove my point to myself, I drove very conservatively for the last tank and got 16.5 mpg. What happened? I replaced plugs and wires around 30k ago. I really don't think it can need that again. I've run Techron injector and system cleaner, every 3000 miles since new. The only thing I can think is maybe something wrong with the MAF. The only mod it has is a Dr Speed Stage 3 CAI. I would appreciate any advice as far as where to look. Last edited by 20SilverGT00; 03-05-2007 at 07:34 AM.

03-05-2007, 02:54 PM	#6
gectek I hate nose hair AKA: John Join Date: Oct 2006 Location: Lubbock, TX Posts: 2,051 Vehicle: 2002 Grand Am GT sc/t	they are all the same, and what you do is take a really good look at it, one piece of the tab will show a part between it, so then take a knife or screwdriver and put it in there and pry the tab out, then push it backward and that will release the fit it has on the filter __________________ If you unscrew ur belly button, will ur butt fall off? Procrastinators UNITE!!!.....tomorrow

03-11-2007, 08:53 PM	#8
Panacea Mmmm Donuts. AKA: Macleod52 Join Date: Mar 2003 Location: Rock Island, IL Age: 40 Posts: 3,160 Vehicle: '09 Malibu LTZ	You have noticed that it's winter out, right? I avereaged 17 to 19 mpg (more towards 17mpg) in the winter time in my 99 GT. Wait till summer and then see what your mileage is. __________________ "Never argue with idiots. They bring you down to their level, and beat you with experience."

03-11-2007, 08:55 PM	#9
cardude007617 mmm turbo boost AKA: Paul Join Date: Dec 2006 Location: Milwaukee WI Age: 31 Posts: 4,870 Vehicle: 2005 WRX Sedan 5 Speed	ya winter does affect the mileage u get, id do that too^^ __________________ http://www.cardomain.com/ride/2565053 -2005 World Rally Blue Subaru Impreza WRX Sedan: Tanabe Touring 3in catback, ERZ bellmouth catted downpipe, catless uppipe, SPT Pink springs, SPT short shifter, SPT intake, stereo, Cobb Accessport stage II, Prosport boost/oil temp/volt gauges, 35%, 17x8 Rota Torques, F/R strut braces It's what makes a Subaru, a Subaru.

03-11-2007, 08:56 PM	#10
gectek I hate nose hair AKA: John Join Date: Oct 2006 Location: Lubbock, TX Posts: 2,051 Vehicle: 2002 Grand Am GT sc/t	dont forget rain also __________________ If you unscrew ur belly button, will ur butt fall off? Procrastinators UNITE!!!.....tomorrow

03-05-2007, 07:32 AM	#2
bballr4567 GAGT - Member AKA: Josh Join Date: Dec 2006 Location: Evansville, IN Posts: 733 Vehicle: 09 Pontiac G8 GT	When was the last time the fuel filter was changed??? I changed mine when I started to get some bad MPG on tanks and I got back the mileage I lost. Also run a few bottle of fuel system and injector cleaner through the system. You prolly have over 100k miles and it might help too.

03-05-2007, 07:35 AM	#3
20SilverGT00 V6 Enthusiast Join Date: May 2005 Location: Winthrop Harbor, IL Age: 36 Posts: 26 Vehicle: 2000 Grand Am GT	Yeah, I have 130k on it. I have run techron injector and system cleaner on a regular basis, however, the fuel filter hasn't been changed in quite a while. I'll definitely do that. Thanks for the advice!

03-05-2007, 07:45 AM	#4
bballr4567 GAGT - Member AKA: Josh Join Date: Dec 2006 Location: Evansville, IN Posts: 733 Vehicle: 09 Pontiac G8 GT	If you tackle this the easiest way to change it is to PUSH the green clip all the way up on the side that is closest to the rear of the car. I would of taken pics of it but I was covered in gas so I just wanted to finish. Forget about the correct technique. Just be careful not to break the clip.

03-05-2007, 08:38 AM	#5
20SilverGT00 V6 Enthusiast Join Date: May 2005 Location: Winthrop Harbor, IL Age: 36 Posts: 26 Vehicle: 2000 Grand Am GT	My car is a 2000 and I believe it has a different clip on the filter, does anyone have any advice on removing the clip?

03-11-2007, 12:37 PM	#7
slickjoe GAGT - Member AKA: Joe Join Date: May 2006 Location: Newark, Delaware Posts: 167 Vehicle: 2001 Red Grand Am GT	I get bad gas mileage, but that's because I drive fast .

03-14-2007, 07:54 PM	#11
aaronandchris GAGT - Newbie Join Date: May 2003 Location: Charlotte, NC Posts: 4 Vehicle: 2000 Grand Am GT	If you have replaced the fuel filter and still get bad gas mileage you may want to look at the fuel pressure regulator. My gas mileage started to get worse and worse and I had almost perfect car maintenance. I replaced the fuel pressure regulator and my gas mileage improved dramatically.

03-15-2007, 02:07 PM	#12
20SilverGT00 V6 Enthusiast Join Date: May 2005 Location: Winthrop Harbor, IL Age: 36 Posts: 26 Vehicle: 2000 Grand Am GT	What should the fuel pressure be when the engine is idling?

03-15-2007, 02:09 PM	#13
Mirage85 MMMMM, BEER, GRRGGHH Join Date: Mar 2006 Location: Home = Knox, Pa: Live / Work= Edison, NJ Age: 38 Posts: 1,116 Vehicle: 2005 Grand Am GT Coupe	I havent seen this mentioned, but hows the air filter? Perhaps try putting the stock filter back on and see if your mileage goes back up? __________________ Mirage Cardomain

03-15-2007, 02:39 PM	#14
20SilverGT00 V6 Enthusiast Join Date: May 2005 Location: Winthrop Harbor, IL Age: 36 Posts: 26 Vehicle: 2000 Grand Am GT	I have put my stock intake and filter back on, mileage is still poor. I also cleaned the MAF and the throttle body.

03-15-2007, 07:24 PM	#16
WeibSunder Got Airway? AKA: Matt Join Date: Jul 2004 Location: Evergreen,NC Age: 36 Posts: 1,337 Vehicle: 06 Dodge Magnum	This might sound totally retarded, but my dad was having the same problem with his little S-10 2.2 4 cylinder, and someone told him to change his thermostat and he did and POOF, his MPG went from 12 mpg back to the 25 that he use to get. You could always try that, worth a shot. __________________ Kenntnis ist Kraft Air goes in and out, blood goes round and round. Any variation in this, is a bad thing!

03-15-2007, 07:46 PM	#17
gectek I hate nose hair AKA: John Join Date: Oct 2006 Location: Lubbock, TX Posts: 2,051 Vehicle: 2002 Grand Am GT sc/t	well rule of thumb is that if you are running a colder t stat then you will lose a little MPG, due to it richening up the regualr mixture __________________ If you unscrew ur belly button, will ur butt fall off? Procrastinators UNITE!!!.....tomorrow

03-24-2007, 08:30 AM	#18
drumking1721 you want it AKA: Paul Join Date: Mar 2006 Location: Kalamazoo, Michigan Age: 35 Posts: 1,591 Vehicle: 2000 Grand am GT Coupe	yea so i changed my fuel filter yesterday....i was 93 octane or higher...and yea when took off the old one and dumped out the gas...it was coming out black...so i think i found my bad MPG problem haha __________________ -Paul

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