OK What Happened to my MPG????

[Shadow14]

I have a '93 GCL 5.2 V8 4WD. I recently replaced the fuel pump & filter and found that the upper console now tells me that instead of getting an estimated 260+ miles out of a tank, it now reads 190. Gas mileage has decreased to 12/13 from 18/24 Highway. I live in New Mexico, and last year while working in Florida I was getting about 24 MPG Highway and it slowly decreased back to the 18 when I got bacl home.

I have replaced the following items:
1. 235/75R 15 Michelin LTX A/T tires running 35#'s of air
2. PCV
3. Crankcase Breather
4. Bosch Platium 4+ Spark Plugs
5. Spark Plug wires
6. Flushed Radiator, new hoses, thermostat,
7. Oil changed every 3,000 miles, flushed, risoline added to 10w40 Pennzoil and filter
8. Cleaned and reoiled K&N air filter

Ok all you afficiando's I have read with great interest the postings on the various subjects on gas mileage and performance. Can anyone give me any ideas as to why this would occur and what should I be checking to correct the problem?

[dksob81]

are you using the BOSCH PLATINUM +4 right now? If so, get rid of them, use CHAMPION 71 (RC12YC).

I was using the Plat +4 and my gas milage went from 13 to 9.6, I replaced with the OEM recommended Spark Plugs (champion) and I am getting 10.4 MPG.

[JDPascal]

Originally Posted by Shadow14

I have a '93 GCL 5.2 V8 4WD. I recently replaced the fuel pump & filter and found that the upper console now tells me that instead of getting an estimated 260+ miles out of a tank, it now reads 190. Gas mileage has decreased to 12/13 from 18/24 Highway. I live in New Mexico, and last year while working in Florida I was getting about 24 MPG Highway and it slowly decreased back to the 18 when I got bacl home.

I have replaced the following items:
1. 235/75R 15 Michelin LTX A/T tires running 35#'s of air
2. PCV
3. Crankcase Breather
4. Bosch Platium 4+ Spark Plugs
5. Spark Plug wires
6. Flushed Radiator, new hoses, thermostat,
7. Oil changed every 3,000 miles, flushed, risoline added to 10w40 Pennzoil and filter
8. Cleaned and reoiled K&N air filter

Ok all you afficiando's I have read with great interest the postings on the various subjects on gas mileage and performance. Can anyone give me any ideas as to why this would occur and what should I be checking to correct the problem?

I agree with the "use champions" idea. Seems these engines like the original design of plug. Plus you can change them every year and be money ahead of using platinium's for 2 to 3 years.

How long has your O2 sensor been in there. My mileage seemed to be decreasing as well. It could have been all the intown driveng but highway driving seemed like it took more too so I did my annual maintenance with a sparkplug change and changed the O2 sensor too - went on a weekend trip with mostly mountain highway miles and averaged 19.3 miles/usg on the computer after resetting the overhead odometer. I also double checked the numbers using my fill amounts and the miles traveled. The numbers were right on!!

I'm not saying that any, all or even most of the increase was due to the O2 sensor, just that after over 120,000 miles on the original, it made sense to me to pop the bucks loose and put one in. They are easy to change (if the engine is cold )

Just my


JD

[TastefullyJul]

About how much does an O2 sensor run? I'm only getting about 13 MPG in my 99 GCL. Thanks.

[JDPascal]

your lookin at about $60 for a "universal" type and $130 for a direct replacement from a jobber parts store like NAPA

We're not talking a guarented improvement here just some planned maintenance that could be done along with regular tune up stuff. The O2 sensor usually fails because of some exhaust contamination from something like antifreeze or non-compatible silicone sealant But years and miles of use also can reduce the sensitivity so I figure a 120k is time for ME. You have to decide whether you want to spring the bucks loose for it or not.

Just make sure that all the other mileage stuff like plugs/wires/dist.cap etc, is done too (either before or along with the O2 sensor)....unless it's failed completely.



JD

[cndoliver]

I replace both of my O2 sensors and my gas mileage dropped I was getting 15.8 now I am getting 13.8 97 GC 5.2

[cndoliver]

Ops Gcl

[rock78230]

If I'm not mistaken your Jeep's original tire size is 215/75/15 and you increased the diameter of your tires significantly. I believe that will play tricks on your odometer, speedometer and gas mileage.