My 2005 Liberty has about 106,000 miles on the odometer right now. As of the last tank of gas I put into her, I have tracked the fuel economy for 100,000 of them (100,299.9 to be precise). Gas prices began to skyrocket shortly after we purchased the rig new in January 2005, so I began tracking the dollars spent and MPGs at each fill up. Being an accounting/finance professional it made sense to put the numbers into Excel and see what the data would tell me over time that might help us manage through the financial pain of rising fuel costs. It also helped give me some basis for some articles I wrote about high oil prices over at
The Truth About Cars.
For the record, my Liberty came with Jeep's Off-Road Group package, which included skids (engine, transmission, drive shaft, and gas tank), tow hooks, Goodyear SR-A P235/70R16 tires, and a 4.10 rear end. At 60,900 miles I changed tires to slightly bigger
245/70R16 Firestone Destination A/Ts. (I did not have the odometer reprogrammed for these tires that have a 2.1% larger circumference, but I controlled for it in the math.)
We took three road trips of exceeding 3,000 miles each as well as several shorter trips that had tanks that were predominantly driven on the highway. I tracked those miles separately. Also, at each fill up I indicated whether I thought I used the A/C more than 50% of the time so I could get breakouts with and without the a/c running.
So this is what the Excel pivot tables tell me:
Miles driven:
- City, no A/C: 48,527
- City, with A/C: 32,303
- Highway: 13,591
- Mixed: 5,620 (this category was for fill ups where the miles driven weren't predominantly City, Highway, or Off-road)
- Off-road: 260
Expenses:
- Total spent on fuel: $16,351
- Avg. PPG (price per gallon): $2.67
- Least expensive PPG: $1.45 (12/13/2008)
- Most expensive PPG: $3.96 (7/9/2008)
Gallons:
- Total: 6,196
- Average per fill up: 17.115
- Maximum fill up: 20.652
Gas mileage:
- City, no A/C: 16.4
- City, with A/C: 15.4 (running the A/C cost 0.95 MPGs)
- Highway: 18.9
- Mixed: 17.3
- Off-road: 14.9 (
fire roads in Utah, not rock crawling)
- Total MPG: 16.47
- Best mileage on a tank of gas: 22.15 (5/27/2005 while driving from Houston to Dallas with family of 4 and luggage - must have caught a tail wind off the gulf)
- Worst mileage on a tank of gas: 11.67 (8/10/2006)
One final note: while I was replacing my
front drive shaft CV joint I removed all of the skid plates except the gas tank skid. In the 8 tanks of gas since doing so I have averaged 17.91 MPG in city driving, an improvement of 1.66 MPG or 10.2%. I think I'll leave them off until gas prices come back down.
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William C Montgomery
The Truth About CarsThe Truth About Guns'05 Sport 4X4, 3.7L - Black | Frankenlift II Premium, JBA KJ Lifted A-Arms 4.5 | Cooper Discoverer A/T3 - LT245/75R16, Load C