Hi, I'm the other member who posted about getting the 10+ mpg.
One thing I should note is your speed. I never drive over 62 mph. That alone might make a substantial difference. I was also traveling with two people, but no dog(s) (we also have a boston terrier LOL).
Theoretically, your 2300 should get better mileage that my 2250 because it has no slide and is therefore lighter.
Regarding oil & filter, Ford's oil is already a synthetic blend. I don't believe that full synthetic and a "hi-performance" filter such as a K&N would make any noticeable difference, or at least that has been my experience.
One thing I am curious about also - does your E-450 have the 6-speed transmission? I ask because I read that there were a few produced with the 5-speed until the supply was used up. If its a 6-speed on your dash you will see a number 4 to the right of N. If that number is a 3 you have the 5-speed. The 5-speed MPG will be less, but I would not think almost 3 MPG less.
I'm really thinking that you should try a run and keep it at 62 max to see what happens.
Also get an app for your smartphone, or GPS, that can verify your road speed. I found that the speedo reads 2 to 3 mph high.
Now, as for the generator. First I'll ask the obvious. Is your generator gas or propane? If propane, are your sure you have propane and that the valve is open. If gas, if your gas tank wasn't at least 1/4 full the generator will not get fuel.
Looking around the internet I see that codes 13 or 14 could point to several issues, including a dirty carburetor.
The generators MUST be run a minimum or 2 hours / month with a load (like A/C) to prevent carburetor varnishing (gunk). If you can get it started again I highly recommend you do that. If the RV is stored at times, you should add a fuel stabilizer (I'll be getting this - https://www.rvupgradestore.com/OnaFr...-p/55-9550.htm
Hope I've helped some!