Is the MPG Gauge on the 2012 accurate?
JK Enthusiast
Joined: Aug 2011
Posts: 388
Likes: 0
From: Salt Lake City, Utah
JK Newbie
Joined: Sep 2011
Posts: 64
Likes: 0
From: Indianapolis
My wife drives our 2012 to work every day, 65 miles round trip. It is mostly on State road with almost no lights. The dash gauge is always pretty accurate for her. Last fillup was 18.6 on the dash and 18.4 calculated. It seems to do better when there is a lot of driving with a steady pedal and worse when there is a lot of accelerating and braking.
JK Super Freak
Joined: Jun 2011
Posts: 1,715
Likes: 11
From: Olympia, WA
Just like statistics, there are many different ways to calculate a metric. You just have to know how its calculated....unfortunately, I don't know how the Mopar ECU calculates the cluster MPG.
Different ways of calculating MPG (not industry standard; just logical mathematical calculations):
1) Miles Traveled/Fuel consumed [This is generally the most used and common calculation]
2) Miles Traveled/Fuel consumed-while not in idle [This calculation discounts any fuel consumed when the Jeep isn't traveling]
3) Average of sampled MPG at different intervals [The ECU will collect a single instant of MPG consumption at different points while moving and possibly while not moving, and then calculate the average of those samples]
4) Historical + Current MPG [Historical or past MPG rates are baked into your current MPG to calculate a life average]
Different ways of calculating MPG (not industry standard; just logical mathematical calculations):
1) Miles Traveled/Fuel consumed [This is generally the most used and common calculation]
2) Miles Traveled/Fuel consumed-while not in idle [This calculation discounts any fuel consumed when the Jeep isn't traveling]
3) Average of sampled MPG at different intervals [The ECU will collect a single instant of MPG consumption at different points while moving and possibly while not moving, and then calculate the average of those samples]
4) Historical + Current MPG [Historical or past MPG rates are baked into your current MPG to calculate a life average]
With accurate fuel measurement and the same distance information that appears on the odometer, there is reason enough to have confidence in the MPG computer. The JK system does not remember previous MPG figures; it starts from scratch at each reset.
I'm sure enough about the JK MPG computer that I would use it to check the accuracy of my manual calculation instead of the other way around.
JK Newbie
Joined: Dec 2011
Posts: 12
Likes: 0
From: Florida
Well i was recently stuck in a traffic jam which dropped my avg MPG down a bit. I've double checked fuel estimators in toyo's, Honda's (2 & 4 wheels) and now the JK. They have always been dead on, although i do live in a flat state (Florida).
