Big drop in mileage

jg45 · **Posted:** Fri Mar 14, 2008 9:54 am

In the last two months I have lost nearly 3-4 mpg. I was getting around 15 in my normal driving situation. Now I am getting about 11. I have made no changes to the Jeep. I have tried switching gas brands, changing the oil and spark plugs, and checking the air filter (Amsoil EAA). I am not getting any codes when using a odb code reader. Is winter gas really that bad or might I be looking for something else to be wrong? By the way, this is a 2003 Sport 4x4 with the 3.7 and 3.73 gears. My driving habits have not changed.

Pote · **Posted:** Fri Mar 14, 2008 12:40 pm

winter gas is one. cold weather is two. I have seen a drastic drop as well in this winter's stats and have also not changed driving habits, in fact, I've probably eased off the skinny peddle alot since first getting the KJ. I'm planning on seeing the original gains again with warm weather and obviously "better" gas in the summer....heck isn't that why it costs a buck more than it did this time last year?? LOL :shock:

Rush345 · **Posted:** Fri Mar 14, 2008 9:31 pm

Winter Gas Check your air filter and tire presure, for such a night and day difference. I would thing their are other factors involved.

jg45 · **Posted:** Fri Mar 14, 2008 10:59 pm

Yeah, first thing I did was order the Amsoil Eaa filter and check tire pressures. I am going to check fuel pressure in the morning. Thinking is that low pressure wouls cause poor injector spray and lower mileage.

Albert · **Posted:** Sat Mar 15, 2008 11:45 am

I have had the same mileage drop problem since winter started. Mine needs plugs now probably.

I ran a bottle of Techron through it to clean the injectors and I think it helped but only a little. It's still a pig.

jeepkj02 · **Posted:** Sat Mar 15, 2008 12:29 pm

Seafoam it....

jg45 · **Posted:** Sat Mar 15, 2008 2:44 pm

Well I didn't have any Seafoam, but I did run about 12 ozs of Marvel Mystery Oil through a vacuum line and let it sit for 30 minutes. Then I took it for a ride around the block. I don't think my neighbors like me anymore. When I worked as a tech we used to use MMO or Auto Trans fluid to do the same thing as Seafoam.

Rush345 · **Posted:** Sat Mar 15, 2008 7:24 pm

Sounds like me a few months back I changed Spark Plugs with Bosch Platinum +4's and while painting my airboxes and grill inserts took a Funnel and poured and entire bottle of Seafoam into the throttle body. About 2-3 hours later after bolting all back together. Fired the Puppy up and I would have done 007 proad with the Smoke Screen I created :twisted:

jg45 · **Posted:** Sat Mar 22, 2008 9:33 pm

Well it seems to have worked. On the first tank after doing the Marvel Mystery Oil my mileage has returned. I also added a bottle of Prestone Fuel System Cleaner to the tank with the last fill-up that I just got done burning through. Engine seems to have more power and responsiveness. Also seems to idle smoother.

tjkj2002 · **Posted:** Sat Mar 22, 2008 9:43 pm

jg45 wrote:

Well it seems to have worked. On the first tank after doing the Marvel Mystery Oil my mileage has returned. I also added a bottle of Prestone Fuel System Cleaner to the tank with the last fill-up that I just got done burning through. Engine seems to have more power and responsiveness. Also seems to idle smoother.

Good to hear.

Oh by the way never put ATF in a fuel injected engines fuel system,big no-no,bye-bye injectors.

jg45 · **Posted:** Sun Mar 23, 2008 8:16 am

We would only run ATF through the vacuum lines never through the gas. IT does a pretty fair job on cleaning the valves and combustion chambers.

Big drop in mileage

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