This is my first post, so bear with me. I also have poor vision so if there are previous post please forgive me.
Besides all of the obvious things, what other things can I do to improve my milage?
Mass air sensor when to clean?
Spark plugs, when to renew? 58,000 now?

 

 

2017 3.6 58,000

 

Advertised mileage is 17 city, 25 highway. What are you getting?

 

10 cfity
14 hwy

 

uses speed density fuel metering so there is no maf sensor.
check your fuel trim readings...if they are within +/- 10% its metering properly.

 

Don't take offense at what I'm about to say because some of these are obvious to some but not to others.

1. Have you had the fuel lines looked over for a leak, if you had a leak you would smell gas so you would have noticed but you have a 30% drop in mileage so whatever the reason is it's significant?
2. Use a GPS and make sure your odometer is correct. If someone put the wrong size tires on it would have an impact on the miles that you put into the miles/gallon calculation.
3. Do you have a lot of extra weight you could drop. I'm 350 lbs sometimes and when I get down to 290lbs I honestly saw a difference in my little economy cars but this van might not care. But shed any weight you can.

Enter the OEM tire size here and the size tire you have and see what the difference may be. That said the odometer can fail for other reasons like a bad vehicle speed sensor but that should trip a check engine light where the wrong tires or pressure in the tires wouldn't.
https://tiresize.com/speedometer-calibration/