So you have changed the oil on this car over 80 times? Amazing!Carbureted 1985 Ford GT Mustang with 5 liter roller cam Windsor, 250,000 mile original owner. Retired to pleasure use with 1,452 miles on last oil change in 2021. Motor has never been apart and never gone over 3K on an oil change. Out at 1/2 quart down of 10W-30 conventual Valvoline. Recent axle upgrade from original 2.73 ratio 7-1/2" ring gear to 8.8" axle with 3.73 ratio improved drivability significantly. Refresh the sump with 10W-30 high mileage Valvoline plus a spike of STP oil treatment. Anticipated hot idle oil pressure improved to 50 PSI at 700 RPM . Happy boy, happy boy.