My 2008 Chrysler T/C limited has averaged 17.5 to 19 city and 24+ highway,but recently that has decreased to 16.5 city and 19 highway. Vehicle has 55 kmiles on the 4.0,there are no codes stored in the PCM,no dragging brakes,transmission engages all gears,engine turns 1750 rpm @ 60 mph. I have owned since new and use 87 octane e10 fuel.The dealer suggested trying different brand of fuel..I normally use Shell,the dealer verified the car has all updates and no fuel leaks. Please advise what should be checked next...thank you

 

Have you checked your tire pressure? Although you mentioned NO Dragging Brakes, how about checking your wheel bearings or CV Joints?

 

From past cars that I have had, the tyres on renewal have worn more at the edges, that's on keeping the pressures right too.
So now I add a few psi to my tyre pressures and well there certainly is a difference in the rolling resistance which can be felt in less throttle at given speeds. In fact it just wants to roll on its own now.
I'm only talking 3 psi here by the way.

 

Original tires were replaced 1 week ago,usually keep 36psi all tires..there is no change in the starting,idle,or performance ...just a big drop in city/highway mpg...with no codes ...should I check oxygen sensor or map?

 

As you mentioned, "there is no change in the starting,idle,or performance" If the Oxygen sensor or map would most likely "effect the performance"! A plugged Cat converter could reduce mpg but that would also show it in engine performance and probably cause codes.

If tires were recently changed is that possibly when the mpg went bad? Are any tires running on the hot side? Possible to have a bad tire with tread squirm problems.

Besides the tire change, did anyone make any brake adjustments?

How about weather changes where you are at? More or less demand on the AC unit??

 

Check your heater/temp. guage is normal, a stuck open thermostat could easily show as excessive fuel consumption. The tyre advice is good too, but check the device used to measure tyre pressure -- I found mine was 3lbs. out! I use 35lb. front (diesel weight) and 33 rear as I carry no heavy loads. Check the petrol you use has NO ethanol/methanol in it, there may have ben a mixture change at your favorite filling station without anyone being told, inc. the proprietor. There have been thousands of complaints about ethanol and its effect on fuel economy. Check if another driver of your motor has bashed a wheel against the kerb and said nothing causing misalignment of a wheel. Get someone with a really good nose to sniff around the motor for possible leaks of petrol. Check the air cleaner is not partially blocked. Have U recently had engine oil changed for synthetic? This can make the fuel consumption worse for a few hundred miles (This is my experience with synthetic talking). Dribbling petrol injectors can cause poor homogenous air/fuel mixing without showing in the errorcodes. If U use an injector cleaner, it won't work by putting it in the tank, it's too weak that way, put it in the fuel filter. Is your gas mileage check by brim-brim method, or just computed readout? The computed one is notoriously unreliable.
Congrats on keeping a fuel consumption record -- apart from saving money, it can predict a coming problem.

Leedsman.

 

I have always figured mpg buy dividing miles driven by gallons to refill to full and compared this to the mpg shown on the display,and the 2 readings are usually within .5 mpg of each other...I have always used 10% ethanol...this is all that is available in my area....I am going to try to find someone with test equip to view fuel injectors "real time".Thank you for the suggestions,the only other work on the vehicle is the front bearing assembles were replaced recently...but I was having the decreased mpg prior.

 

Front bearing assy replaced! You van has very low milage to have had the bearing assy's replaced (unless you have some harsh driving conditions) What indications did you experience (if you care to share) led you to the bearing assy's problem. Thanks.

 

The clue was a roaring noise that changed to a higher pitch as speed increased,the van still had the factory tires so I rebalanced and rotated the tires which made no change in the noise,I have extended warranty so I went to the dealer and they found the drivers side bearing assembly causing the noise..they did replace both front assembleys...there was no noticeable vibration...just a whine that over several weeks continued to get louder. We have owned since new,May 2008....and the van has never been driven in any condition,or in any way that would cause bearing failure.

 

There was a Service Bulletin number 02-004-12 concerning replacing front wheel bearings due to premature failure on 2008-2009 vans built before 10-15-2010. They also extended the warranty for vehicles in cold regions to 5 years or 90,000 miles.

George