hey msm0075 you might want to check fuel press regulator can be making it run too rich. my 90 2.3 gets 420 to 430 miles to a tank with 210 000 miles on it
the HSC and OHC are two completly diff engines the HSC has the intake and exhaust on the side. hsc is a pushrod eng and it never had an aluminum head. the aerostar used the OHC mostly with a 5-speed
you may wont to check for a bad fuel press. regulator. temp dosn't affect my milage. temp gauge rarely come off the 130 mark unless stopped in traffic. i put 3.27 gears in for all my hiway driving get 410 to 430 miles to tank at 70 to 80mph.