Gas Milage
Thread Starter
Heel & Toe
Joined: Aug 2003
Posts: 17
Likes: 0
From: woodbine ga
Gas Milage
Why am I only getting 20 mpg at best highway driving thats computer and calculator. Had car at a dyno shop for testing they ran eng. ****. exhaust gas they said it would pass emisions test if I had to. The car has no cats free mods and the ford 22# injectors I thought it was running rich but it is not.It has fresh tune up msd wires top end was off and cleaned and throwing no codes any ideas what to look at. thanks :chevy
Team Owner
Joined: Mar 2001
Posts: 66,677
Likes: 86
From: Santa Cruz CA
St. Jude Donor '15
Re: Gas Milage (gary samuel)
How long have you had it? Has it always gotten that mileage?
Maybe you have a really low rear end gear that someone changed to. That would decrease your MPG some. :confused:
Maybe you have a really low rear end gear that someone changed to. That would decrease your MPG some. :confused:
Team Owner
Joined: Dec 2000
Posts: 90,675
Likes: 304
From: SE NY
Cruise-In II Veteran
Re: Gas Milage (gary samuel)
Sounds like all is well with the motor but you can use the ECM's diagnostic mode (on my site, link in sig. below) to see if the ECM is going/staying closed loop.
Also verify tire pressure is in the low-mid 30s as rolling resistance can add up.
When you do the mileage check, use cruise on a flat stretch of highway.
Does instentaneous & average mileage show the same data?
Also verify tire pressure is in the low-mid 30s as rolling resistance can add up.
When you do the mileage check, use cruise on a flat stretch of highway.
Does instentaneous & average mileage show the same data?
Race Director
Joined: Oct 2002
Posts: 10,864
Likes: 196
From: Southern CA
Re: Gas Milage (gary samuel)
I'd love to get 20 mpg, best I ever did on a tank was about 14.8 mpg. I do like to keep the tach in the power zone, though, I don't even know if 5th and 6th are there.
Thread Starter
Heel & Toe
Joined: Aug 2003
Posts: 17
Likes: 0
From: woodbine ga
Re: Gas Milage (gary samuel)
Thanks for the sugestions, the gears are 2.59 , auto, the shop said it stays in closed loop highway driving. I just read alot of posts here saying your getting 25+mpg hwy. I have had the car for 6 months so I dont know the best gas milage it ever did get.
thanks :chevy
thanks :chevy
Le Mans Master
Joined: May 2003
Posts: 5,362
Likes: 3
From: Delray Beach FL
Re: Gas Milage (gary samuel)
You may want to look at replacing the O2 sensors. I just did that on my 93 with 156,000 miles on it and my fuel economy went up. If you have a lot of miles, it may be something you want to look at.
:cheers:
:cheers:
Thread Starter
Heel & Toe
Joined: Aug 2003
Posts: 17
Likes: 0
From: woodbine ga
Re: Gas Milage (gary samuel)
Forgot to mention that I just replaced a new o2 sensor with another new one. Are there any other things to check, would a coolant temp on the egr have an effect. The mechanic installed champion platniums which im going to change out for the ngk this weekend. :chevy
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Team Owner
Joined: Aug 1999
Posts: 24,017
Likes: 634
St. Jude Donor '10
Re: Gas Milage (gary samuel)
How fast are you driving?
At 65mph I get 26mpg. At 80mph, I get about 21-22.
My stock 85 never got over 22-23 at 65 or so, and above 75 I never got better than 20-21.
At 65mph I get 26mpg. At 80mph, I get about 21-22.
My stock 85 never got over 22-23 at 65 or so, and above 75 I never got better than 20-21.
Team Owner
Joined: Dec 2000
Posts: 90,675
Likes: 304
From: SE NY
Cruise-In II Veteran
Re: Gas Milage (gary samuel)
I think it is a tuning issue; use the self test to double check the closed loop issue.
My bone stock '88 (down to the Fram air filter) pulled 29mpg on the drive from Phoenix to NY when I was driving the car home. Now, with current mods on flat highway at 65mph and cruise set it pulls 31-32mpg.
I would look at that closed loop verification and maybe check for a leaking injector and check spark plug condition as well as base timing and such, even though it can currently pass emissions.
My bone stock '88 (down to the Fram air filter) pulled 29mpg on the drive from Phoenix to NY when I was driving the car home. Now, with current mods on flat highway at 65mph and cruise set it pulls 31-32mpg.
I would look at that closed loop verification and maybe check for a leaking injector and check spark plug condition as well as base timing and such, even though it can currently pass emissions.
Melting Slicks
Joined: Mar 2002
Posts: 3,252
Likes: 6
From: The Colony Tx
Re: Gas Milage (gary samuel)
I have an 88 coupe auto and I routinely drive from KC to DFW and on the trip down I average just over 26 mpg. On the return trip I usually get around 25.4. I have made this trip at least 15 times in the last 3 years and the MPG rarely varies.
On my last trip, 1400 miles including intown of 400 miles, I had an average of 25.4 mpg.
On my last trip, 1400 miles including intown of 400 miles, I had an average of 25.4 mpg.
Le Mans Master
Joined: Oct 2000
Posts: 6,362
Likes: 30
From: Oak Harbor WA
Re: Gas Milage (froggy47)
I'd love to get 20 mpg, best I ever did on a tank was about 14.8 mpg. I do like to keep the tach in the power zone, though, I don't even know if 5th and 6th are there.
Thread Starter
Heel & Toe
Joined: Aug 2003
Posts: 17
Likes: 0
From: woodbine ga
Re: Gas Milage (gary samuel)
I will check all of the recomendations you-all have made. Sometimes the car gets alot less gass milage depending how crouded interstate is.
thanks :chevy
thanks :chevy
Racer
Joined: Sep 2000
Posts: 294
Likes: 0
From: Princeton Texas
Re: Gas Milage (gary samuel)
Have you actually calculated the gas milage using actual miles driven divided by quantity of fuel used? I see that you have changed injectors. I read in a post a while back the computer calculated MPG can be erroneous with aftermarket injectors. The best way to check is fill the car up, take a trip for a known distance, refill the tank and do the calculations. An error in your speedo or different tire size can also throw off the computer calculated values.
FP
FP