How many miles should I be getting out of my 93 J30? It has about 174450 miles on it. I've had it for about 8 yrs now and put 54,000 miles on it. I get about 280 miles pushing hard out the tank. Also my fuel stick on the dashboard never reaches full after i gas up. It usually stays about 2 lines short of F. Any reason for that? I've decided to keep this car after I replaced my 96 I30 with a 06 M35X.

Ours runs a little over 2 hrs per fill up, that's about 8.5 gal per hour when operated in track competition.

Sorry couldn't stop myself from posting. I did not drive the car long before making it a track car but I never remember being pleased with the city MPG.

On Octane 94, I get 19mpg city and 22-25 mpg(depending on the use of cruise control) highway. If you're using regular gas (anything below octane 91) your mileage will be poor.

The highest octane available in Arkansas is 91 with up to 10% ethanol. I have only put premium in this car. I have never seen 19mpg as you get on the low point in the city. Do you have any idea why my fuel gauge won't go the the top. I can fill it up until the pump clicks multiple times to get as much in there and that gauge stays 2 notches below full. How big is the gas tank anyway?

Have you replaced the Plugs, Air Filter, Fuel filter ect ??
All those will affect mileage, As well as a defective Knock sensor.
It will not cause a Check engine light , but you can tell as the acceleration below 3K rpm is sluggish.

Plugs are Platinum, Air Filter is clean, never changed fuel filter but will look into that. How often should a fuel filter be changed?

Really depends on the debris in the tank.
What happens is, a few years ago we were forced to use Ethanol.
When that happened it started breaking loose crud in the tank.
I did my first when I got the car, and it was VERY dirty.
Did the next one with my next oil change and it was better but still dirty. (Gas poured out of the "In" side)
I replaced every 10K Since.
If you can get the ECU codes read that will help narrowing down any issue's.

I took my car to the mechanic and got the fuel filter changed. He said it was basically 100% obstructed as I watched him blowing hard trying to get the fuel out the other end. This should help and I will get the ECU condes pulled probably next week to see if anything comes up. Thanks again for that heads up.

clemson99 wrote: Do you have any idea why my fuel gauge won't go the the top. I can fill it up until the pump clicks multiple times to get as much in there and that gauge stays 2 notches below full.

The ballast in the tank at one point likely got stuck and may now have to be re calibrated. recalibration is a pain in the a$$ exercise.

clemson99 wrote:The highest octane available in Arkansas is 91 with up to 10% ethanol. I have only put premium in this car. I have never seen 19mpg as you get on the low point in the city. Do you have any idea why my fuel gauge won't go the the top. I can fill it up until the pump clicks multiple times to get as much in there and that gauge stays 2 notches below full. How big is the gas tank anyway?

Some brands of gasoline aren't as "clean" as others and over time can affect fuel gauge readings. Even if my needle makes it all the way to the F, after a fill up (19 gal tank capacity) it drops the fastest during the first 50 miles of driving.

A pair of new O2 sensors could easily get you a couple more mpg on the highway, and possibly help extend catalytic converter life too.

GerryO,

I have the same issue of the fuel gauge drops fast for the 1st 50 miles as you descibed. Why is that? Also how often should o2 sensors be changed? I never had that done before.

Good call Gerry, Forgot to mention O2 Sensors.
Nee to do mine someday.

clemson99 wrote:GerryO,

I have the same issue of the fuel gauge drops fast for the 1st 50 miles as you descibed. Why is that? Also how often should o2 sensors be changed? I never had that done before.

I think part of it's related to the shape of the fuel tank, with it being slightly tapered near the top and also to the less sensitive upper portions of the conductive sensing mechanism that are fully submerged only when the tank is completely Full, a condition that doesn't last for long.

Last changed both O2 sensors at about 175K miles, after the CEL light started coming ON, upon slowing and after driving non-stop about 100 miles at freeway speeds. Believe the exhaust also starts to smell a bit funky when an O2 sensor is starting to fail.

Found driver side is easier to change than the passenger side, and had to use an old sensor to chase galled inner threads of the threaded reducer bushing (removed it along with the sensor) on the passenger side.

Car is running a lot stronger since I got new fuel filter put it. When I get the ECU coded I'll let you know what comes up.

I was getting 26 MPG on highway road trips. Considerably less in town.

I just figured out that I am getting 17 mpg in the city. I filled up yesterday for the 1st time after the new fuel filter and adding Redline to the gas tank. Let's see if I can do better in the city now.

This is becoming nerve racking as I can't trust my fuel gauge anymore. Yesterday my gauge got under the last tick on the fuel gauge and I ran 322 miles out the tank. I was only able to get 14.9 gallons in the tank after it clicking numerous times trying to get more in there. Then the gas gauge only went to 2 clicks below the full level after all that. I heard the tank holds 18.5 gallons. Does that mean I still had 3.5 gallons in there when the gauge hits the bottom? If so that's about 60 more miles easy I could get. Any thoughts?

I thought I read in my owners manual that it was 19, but 18.5 is close enough! The gauge will drop below the last tick and will keep going for about a gallon or so until the gas light turns on. At this point you have roughly 2.5 - 3 gallons until you are running on fumes. I have ran it until empty on a few occasions and got another 60 - 70 miles after the gas light turns on. Some quick calculations:

322 miles / 14.8 gallons = 21.76 mpg

21.76 mpg * 18.5 gallons = 402.5 miles to a full tank

I just took a trip to Las Vegas this past weekend and from Phoenix to Vegas with the cruise set at 85 - 90 I was getting 24mpg. I cant tell you how much I love this car, 16 years old with 230,000 miles and it still is more efficient than my girlfriends 2006 M35!

thanks for the reply "J". I will keep that in mind on the next tank. I have a new found love of my 93 J 30. It has 174,500 miles on her and going strong. I saw that dig against your girls 06 M35. I actually have a 06 M35X also that replaced by 96 I30 that had 288,800 before I got rid of it. I'm just an Infiniti lover.

Generally not a good idea to run the car till the gas tank is empty or running on fumes. Gulping fumes or air has been known to destroy the fuel pump/fuel sending unit and it is a PITA to replace, you have to remove the back seat to get at it.

thanks Driver. I won't run it down to the bottom but now I know that I don't have to make a bead straight to the gas station.

Yeah the reason I let it go down that low was because I was having fuel pump issues and ended up having to replace it. And I don't know about it being a pain in the a**, I got to it from the trunk and had it out in 5 minutes.

go back to the NGK Iridiums that are meant for the car. the platinums run too hot especially the +4.