MPG - Advise?
Thread Starter
Instructor
Joined: Jul 2008
Posts: 178
Likes: 4
From: Chandler AZ
MPG - Advise?
I recently bought a 96 LT1 with 100k on it.
I just figured it out today, I'm getting 18 miles per gallon.
I drive almost exclusively on the highway, about 70 mph.
Doesn't this seem low?
Any suggestions? Fuel injectors maybe?
I just figured it out today, I'm getting 18 miles per gallon.
I drive almost exclusively on the highway, about 70 mph.
Doesn't this seem low?
Any suggestions? Fuel injectors maybe?
Melting Slicks
Joined: Feb 2008
Posts: 3,286
Likes: 6
From: Palm Beach
How are you determining the 18 MPG. If it is from the display, it must be verified.
If it is truly 18 MPG, that is low. My 96 LT4 gets about 26 at 70 MPH.
Your 96 is OBDII.
A laptop scanner to do a little datalogging would help. I use Autotap.
If it is truly 18 MPG, that is low. My 96 LT4 gets about 26 at 70 MPH.
Your 96 is OBDII.
A laptop scanner to do a little datalogging would help. I use Autotap.
Last edited by MK 82; Sep 8, 2008 at 08:03 PM.
Drifting
Joined: Aug 2004
Posts: 1,430
Likes: 2
How are you determining the 18 MPG. If it is from the display, it must be verified.
If it is truly 18 MPG, that is low. My 96 LT4 gets about 26 at 70 MPH.
Your 96 is OBDII.
A laptop scanner to do a little datalogging would help. I use Autotap.
If it is truly 18 MPG, that is low. My 96 LT4 gets about 26 at 70 MPH.
Your 96 is OBDII.
A laptop scanner to do a little datalogging would help. I use Autotap.
Pro
Joined: Jan 2004
Posts: 649
Likes: 56
From: TX
Not necessarily. I presume you have an automatic. EPA rated at 15/23. If you have an optional performance axle ratio - 20 mpg would be about right. You're only 2 off from that.
Do you in fact have a performance axle ratio?
Do you in fact have a performance axle ratio?
Burning Brakes
Joined: Nov 2004
Posts: 781
Likes: 0
Two words...
sixth gear
Sorry,
seriously though, I would try some typical tune-up stuff first.
Spark plugs and oxygen sensors (start with just the front two).
Oh yeah, does the car have any mods? RPM at 70 MPH?
Test/check for convertor lock-up, maybe.
sixth gear
Sorry,
seriously though, I would try some typical tune-up stuff first.
Spark plugs and oxygen sensors (start with just the front two).
Oh yeah, does the car have any mods? RPM at 70 MPH?
Test/check for convertor lock-up, maybe.
Last edited by 500hp; Sep 9, 2008 at 09:22 PM.
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7th Gear
Joined: Aug 2008
Posts: 7
Likes: 0
I took a slow ride to the dealer in the next town earlier this week. First time on the road since scouring the intake of carbon, and new plugs and wires. It was already running okay before; just cleanup and maintenance.
I set cruise at 54mph (country roads, level), reset mileage, drove in the parking lot at the dealer a few minutes, then came back cruise set at 54 again. It was about 29 miles.
When I pulled in my driveway, it was at 32.2mpg. 70 would probably bring it down to 28. City/highway combined? Probably 14
.
Combined would be 23 - 24 I'm guessing...
I set cruise at 54mph (country roads, level), reset mileage, drove in the parking lot at the dealer a few minutes, then came back cruise set at 54 again. It was about 29 miles.
When I pulled in my driveway, it was at 32.2mpg. 70 would probably bring it down to 28. City/highway combined? Probably 14
.Combined would be 23 - 24 I'm guessing...
Team Owner
Joined: Feb 2006
Posts: 24,460
Likes: 7
From: sw Ohio
Its possible that someone may have swapped out the rear gear for a taller ratio. A 4.10 gear in the rear would certainly drop you down in mpg at highway speeds. Let us know what your rpms are at 70 mph.
Thread Starter
Instructor
Joined: Jul 2008
Posts: 178
Likes: 4
From: Chandler AZ
Oh, also, I have an obdii scanner, and the car isn't throwing any codes, except for the SYS blinking every 15 seconds. Do I need to unhook the battery to reset the SYS code? Anything SYS-related that could effect mileage? Thanks in advance for any responses!
Le Mans Master
Joined: Aug 2004
Posts: 5,141
Likes: 7
From: Metairie Louisiana
Is it an auto or a manual transmission? I get 16.1mpg overall average and 21-23mpg on the highway at 70mph. If you have an auto and that's your average overall rating I'd say it's pretty good. If you are looking for better mileage check the basic stuff.. tire pressure, airfilter, plugs, cat's, O2 sensors, MAF, etc..
Pretty soon I'm going to do it all, sparks, plugs, O2, maybe fuel injectors. Thanks everyone!
Drifting
Joined: Jan 2006
Posts: 1,740
Likes: 2
From: Winchester Virginia
How about resetting your fuel button while your on the highway driving at speed. I've noticed that if I drive around town for extended periods of time and the computer averages less than 20mpg, when I get on the highway my fuel usage rate is higher than when I reset and allow the computer to recalculate above 28mpg or so. I've gotten over 500 miles on a tank of gas in my 91 driving from Northern VA to Detroit and the display registered 29mpg average the whole way. After riding around for the Woodward Ave for the weekend then headed back. I didn't reset until mid-Ohio, I had to stop and get gas well before I got home. Not sure if anyone else has experianced that, but I did!
R/Noland
R/Noland