What would caused myJeep to burn excess fuel only averaging 9 miles to a gallon.

Just fill the car's tank up and run it for 100 miles and then refill the tank to full again. Check the miles run and fuel amount added and then check the gauge position before and after the fill and calculate the Miles per gallon. This manual check will show if the fuel gauge is not reading accurately and if you are burning excessive fuel. If you are burning excessive fuel have the engine scanned as the computer may be generating some fault codes which will help point to the possible causes of the excessive fuel usage.

Gas mileage depends on several factors.
Average for a 2003 model is 17 city and 27 highway.
So if you combine those numbers, you could expect an average of 22 mpg which would be 4.5 gallons in 100 miles.

You would need to check with a local garage for repair prices.
To find your average mileage, fill up the tank, write down the mileage, then do it again at around 200 miles. Divide the mileage traveled by the number of gallons used. I would recommend filling up after you have used about 8 or 9 gallons to prevent running out of gas. You can't go by the federal mpg numbers because everybody drives differently.

The Fuel Economy of the 2004 Hyundai Santa Fe is listed as being 16 mpg in the city and 22 mpg on the highway.----------------------------------------------------------------------------------
Digiprog3 Odometer Correction Tool

Average for a V6 engine 2 wheel drive model is 20mpg. That is 20 miles per gallon US.
If you have an 18 gallon tank, you could expect 180 miles on a half tank of fuel. Again, this is US measurements.

That should be acurate to about a few miles, it take the average miles per gallon to find its reading, a good test would be to put a gallon of gas in the car and drive until it tells you you have 2 miles left and then go get gas, this way if you run out you will be able to put gas in, i think this would be a good way to test the system. good day.

check airfilter

an air leak would weaken the mix of fuel to air so giving you better fuel efficiency but a poor power output.
was my last answer not to your liking, re **** fuel consumption on all fiat/alpha cars.but it is true, ask any owner........14.7 average mpg.......£205 road tax.....(tax it for a year and quadruple its value...)

Have you changed the fuel filter? I know it sounds weird but a plugged filter will make a truck use more gas. The computer tries to compensate for less fuel by commanding the injectors to open longer. Also a plugged filter will cause excess back pressure on the fuel pump making it loud.. Good Luck.

My Answer:

Poor gas mileage can be a result of many many things.

First of all you need to find out what is the factory normal gas mileage for your model year Jeep SUV. It should have said on your window sticker if you bought it brand new. If you are a 2nd or 3rd owner then a Jeep dealer would have info. Google search will tell you as well, and only takes a couple minutes to find.

I did a quick Google search and for a 2003 Jeep Grand Cherokee with a (4.7L V8 engine) the average mileage is roughly 14 mpg.

Not sure what engine you have as to options, etc?

How you drive will greatly change that number up or down depending on a number of driving and driver variables.

A few being -

Driving habits?

Tire pressures?

Engine tuned up?

Lube & oil/filter changes (every 5,000-7,500 miles? Air filter changes (every 10,000-15,000 miles)? Read your auto manual for exact recommended intervals.

How many people in the SUV on average?

Are you towing anything?

Type gas you are burning - BRAND? (See injectors below)

Area you are driving in (hills and valleys verses flat out,
etc)

Jeeps in general don't have a good track record for great mileage, and rough engine idling is always a clue that your fuel injectors are dirty. Typical on all Jeeps with port fuel injection systems! On Jeeps with dirty fuel injectors your mileage will go way down accordingly. If your not putting at least a 12 oz bottle of say Walmart brand Super Tech Fuel Injector Cleaner (~ $1 each) in your gas tank religiously every logged 1000 miles, or every 2 tank fill ups, then you are just inviting dirty fuel injectors and POOR fuel economy!

My 1993 Ford XPLR with a 4L V-6 engine (and ~ 160,000 flawless driven miles) gets roughly 22 miles per gallon on the highway with cruise control on, and about 17 around town on average. I religiously put a 12 oz bottle of the above injector cleaner in my gas tank every 1000 miles!! Of course I do all my own tune-ups, general repairs, and suspension maintenance (shocks, O2 sensors, trans oil changes, lube & oil/filter changes, code reading and clearing, etc) myself and it shows! I don't trust repair shops except for say Tires and Balancing at SEARS.

Hope that helps ease your mind about gas mileage as it relates to your Jeep there.

Frank