You will be hard-pressed to get the dealer to correct it.

Since the fuel economy at highway speeds is marginal, I think you can test it at steady state conditions, focusing your diagnosis in 4 areas. An ELM327 real time odb2 gadget off ebay ($20) will help you view 8 pages of vital engine statistics in real time on a laptop, as you drive down the highway. Maybe let somebody else drive lol:

1) occasional misfire due to some sort of ignition issue (should throw code)
2) excessively rich A/F mixture issue due to O2 sensor out of calibration or failed temp sensor always thinking the engine is cold (the computer can't necessarily detect either problem, so good luck with that...you may not get any check engine codes)
3) transmission failing to lock-up in 6th gear (could be temp sensor or transmission issue). This can be confirmed with good feel and a sharp eye on the tach, verifying appropriate RPM with zero torque converter slip compared to road speed. If no converter lockup, an engine temp sensor could be the problem. Converter Lockup is cpu controlled, only enabled after engine reaches normal operating temps. Efficiency suffers 10% or so with no lockup.
4) dragging brake due to sticking caliper piston, rusted/stuck emergency brake, rusted/stuck floating caliper mechanism, collapsed hose or bad ABS control valve. Rusted & jambed caliper hardware is quite common & the gas mileage will plummet. Brake drag can be diagnosed fairly easily with a jack. Do all 4 wheels spin freely by hand in neutral? Premature brake wearout is a sure sign.

 

Just looking down the road. You can run the numbers (looks like you like to) but say the dealer won't touch it and you kept the van for 3-5 years living with the lower fuel mileage. Compare those costs to the added costs of buying another vehicle. Which looks better? I'd bet keeping the van will win.

Now compare the costs of throwing money at it to fix it or leaving it as is. Of course, it all depends on how much money you put into it but at what point will the payback happen meaning the amount you put into it to fix it finally equals the amount you saved in fuel costs due to increased fuel mileage?

 

My problem is, I replaced a 2004 Honda Pilot (with exactly the same MPG) that I owned outright with this van that I now pay $400 every month for, for 4 more years...... The Dodge was supposed to get me much better mileage than the Pilot but that is not the case at all.

Also, I have a 5 year extended warranty. I'd like to think that any costs required to "repair" my van would be covered.

 

Maybe you have a set of poor fuel economy tires.

 

Who gave you that idea?

 

Why should a caravan get "much better" fuel mileage than a pilot when both vehicles have huge frontal area, poor aerodynamics and weigh the same? I would not trade a small SUV for a porky 4500lb minivan expecting miracles wrt efficiency.

Anyway, the 4th possibility for poor gas mileage involves fuel type. I didn't note what fuel you're using or where you live. Alcohol additives cause fuel economy to drop a lot. Fuels with reduced octane can too because the knock sensors may back off spark advance. Canada is especially a problem because companies are allowed to spike fuel with ethanol beyond 10% and the fuel quality is not managed as well as in the USA. You could easily lose 15% economy running sub-par fuel.

PS: Tire type will not affect fuel economy more than a couple percent. Tire pressure will though...lots of folks neglect to keep pressures up. Hopefully you investigate each possibility I outlined. I worked as a lab test engineer for a major petroleum company and know a bit about this topic.

 

The sales rep told us we'd get mid 20s MPG which is what I am hearing from other Caravan owners as well. My research showed me as well that mid 20s was about right for this van. The sticker was higher than that, but we all know better than to believe the sticker.

My Pilot was of course 8 years older than the van so replacement based on mileage was not the only factor.

Most of my fill ups are in Canada. I do live in a border city and have the ability to fill up in the USA. I try to always buy gas from the big players. Esso, Petro Can, Shell, BP etc.... On rare occasions I have to fill up at an off brand station.

I check tire pressure regularly and have fluctuated it up and down to see if I can find a sweet spot.

RA

 

All Dodge Grand Caravans are built in the city I live in. You cannot shoot a hockey puck on the street and not hit one in someones driveway. I asked and spoke with dozens of people about this van before I purchased it

I saw numerous fuel logs and records from friends and strangers alike and everyone I saw put the Caravan 4 - 6 MPG higher than my Pilot.

I thought it was a safe move.....

 

20500 km - 12738 miles - might be time for a NEW air filter. I just changed my air filter to a new one and my hwy mpg went from 25.4 mpg avg to 27.1 mpg avg doing 63 to 70 mph on my 2005 3.8L D.G.C. SXT with tow package.

The FRAM Tough Guard air filter is a good one to get; I bought mine for $10.88 at a SuperWalmart.

 

He is already getting 23.81 MPG. He is only losing 1.19 mile per gallon from the advertised 25 MPG. The widow sticker clearly states that the fuel economy ranges from 19-24 MPG. He should expect 20 mpg for combined highway and city driving. Anything above 20 mpg will depend on how you drive your van.