Re: '06 Freestar HORRIBLE Mileage
Synthetic oils will free up a couple HP that would otherwise be lost due to frictional loss.
Driving speeds and style can greatly contribute to lower mileages/range. Tire pressure and tread style are another possibility. Thicker treated tires with some sidewall bite will be more inefficient at higher speeds. Running tires overinflated (even 1-2psi) won't necessarily help with mileage as it lifts up the vehicle ever so slightly thus increasing drag and you run the risk of blowing the tires.
It's minimal here, but weight in the vehicle also plays a role. Less weight, equates to better throttle response and less throttle is needed to get up to a similar speed. If you run with all your seats in, that adds 250lbs or so right there. Don't need that third row? - store it in the shed/garage (wrapped in plastic/bags to prolong fabric life).
Exterior enhancements such as roof rail bars, side steps (skirts) and even wider tires (I believe the Freestars came with 3 tire sizes/widths depending on model Base/Sport SEL & Limited) can hamper mileage. Larger diameter wheels are heavier and again, can cost you in some mileage although it's rather miniscule.
Lastly, does this other Freestar owner drive the van until the reserve fuel kicks in (fuel light comes on) or does he fill up before then? It's easy to get another 75km after the fuel light comes on and having a few litres left to spare before hitting up a gas station. If you both fill up with 80L at a time, then check the variables above.
There are a lot of variables to consider, right down to the fuel brand/type/octane used.
'00 Durango R/T 360ci 290hp (modded); 138,500m
'06 Pontiac G6 GT 3.5L 220hp; 44,000m
'12 Chrysler 200 Limited 3.6L 283hp; 13,000m
'99 Taurus 3.0L 2V Vulcan 145hp; 154,300m - Traded
Amsoil in all vehicles!