Holy bad gas mileage!

CTjeeper16 · **Posted:** Wed Jun 27, 2007 11:46 am

Ok, well when i filled up, the needle was resting on the thing that keeps it from falling all the way down. as far as how much gas is still there when that happens, i dont know, but I wouldnt like to find out how much more there was.

In other news, checked the air filter, clean still, as I changed that and the oil about 1,000 miles ago. I'm thinking it was just a fluke event because I seem to be back around 17 mpg combined, maybe a tad over that.

So who knows. at this point, I'm checking prices on swapping out the muffler for whatever minimal benefits that will provide.

cmohr · **Posted:** Wed Jun 27, 2007 10:13 pm

I know it sounds wacky, but, if you are running bigger tyres and have the v6 auto, you should really look at getting your speedo recalibrated.

1- bigger tyres record a lower speed and distance, so if you travel 100 miles on your odometer, you have probably gone between 105 and 108 miles in actual fact, that will give you a false mpg for a start.

2- the speedo dosn't just tell you how fast you are going. The ECU in these things uses that info to make a whole bunch of calcuation for the engine and gearbox, things like fuel mix, spark timing, what gear to be in. When the info the ECU receives is different to that in the computers data table the ECU tries to make compensations to make the info match, but, it never will, because the speedo is out. You will use more fuel, have less power, and, the car will hunt around gears tring to get things to go right.

I run 245/75/16's in a MTR, and had heaps of issues, bad gear changes, auto constantly hunting around in the gears changing up and down at inappropiate times, torque coverter locking up at too low a speed, real bad milage, and a real loss in power. Had the speedo recalibrated to the correct setting for the tyres, WOW, power BACK, economy BACK, no more funny gear changes, like driving a new car.

This REALLY worked for my KJ. Couldn't be happier now.

Video Guy · **Posted:** Thu Jun 28, 2007 9:54 am

cmohr wrote:

I know it sounds wacky, but, if you are running bigger tyres and have the v6 auto, you should really look at getting your speedo recalibrated.

Thank you for bringing up this topic. It's definitely a factor.

What's involved in the recalibration process? Specifically, what information, if any, does the technician need from the customer?

I've thought of doing this. How much would it cost? Can someone other than a Jeep dealership do the job correctly?

steepcreekfreak · **Posted:** Thu Jun 28, 2007 12:31 pm

You could get a truspeed from superlift. they are about 200 bucks or so. They allow you to set two different tire sizes so you can run streets and meats. They connect beteen the rear wheel speed sensor and the computer. Real speed correction. I am thinking about getting one installed this fall.

Here is a link...

http://store.summitracing.com/partdetai ... 02&FROM=MG

tjkj2002 · **Posted:** Thu Jun 28, 2007 1:10 pm

steepcreekfreak wrote:

You could get a truspeed from superlift. they are about 200 bucks or so. They allow you to set two different tire sizes so you can run streets and meats. They connect beteen the rear wheel speed sensor and the computer. Real speed correction. I am thinking about getting one installed this fall.

Here is a link...

http://store.summitracing.com/partdetai ... 02&FROM=MG

True speed is a total ripoff! Just beware of it,known poeple to have many problems with it and it's way overpriced.Here is a much better product-----http://www.dakotadigital.com/index.cfm/page/ptype=product/product_id=126/category_id=287/home_id=59/mode=prod/prd126.htm-----And can be used in many configureations,cost over half less,and can be adjusted while driving.

chefdab · **Posted:** Thu Jun 28, 2007 4:17 pm

As for having the speedo recalibrated by the dealer, I believe all they need to know is how many revolutions per mile the manufacturer claims for the particular tire you are running. Some people have had the dealer do it free, others have had to pay a small labor fee. It shouldn't take them more than ten minutes to do it.

cmohr · **Posted:** Thu Jun 28, 2007 9:42 pm

Have a look thru this thread, I have quite a bit of info there on it.

http://www.lostjeeps.com/forum/phpBB3/vie ... hp?t=21020

Depending on the year, the ecu itself has the tools for setting tyre size. Some have a Rev per mile setting, some have a tyre size setting (ie- 235/70/16 or 245/70/17 and so on) some unfortunatly have no adjustment. To get the rev per mile have a look at the BF Goodrich site and their tyre spec charts they have rev pewr mile under static load. Anyway as I said heaps of explaination in my thread, and makes a big difference.

cmohr

slikjr · **Posted:** Fri Jun 29, 2007 6:16 pm

I'll ring in here... My 02 Liberty was running a 2.5" lift and 265/75 MudTerrains. On the highway it would get between 16 and 12, depending on wind. The wind really plays a factor with all Jeep vehicles.

With my 2007, it has the same 2.5" lift but only 245/75 Timberline MT's (for arguments sake, same tread as MudTerrains). So, the tires are little smaller, but not a lot. I am getting 26mpg consistantly on the highway! And that's with a few hundred pounds of luggage. The engine has stayed the same in the Liberty over the years but they have obviosuly done some subtle changes to it to improve fuel mileage.

I am very happy with the fuel mileage of the 2007's. They seem to be getting a lot better fuel mileage all across the baord.

slikjr · **Posted:** Fri Jun 29, 2007 6:17 pm

and my speedo is not changed for the new tires

Holy bad gas mileage!

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