Re: Ford 9" rear end oil change! additive a must?
I use the additive even with synthetic fluid if you want to go that route. As good as synthetics are, most state you don't need the friction modifier but I use it anyway. After adding synthetics in the gears, transfer case, transmission and engine i've noticed a 4-5% increase in fuel economy in my dodge and just trans and engine oil in my taurus I've seen as high as 10% increase on the highway. Synthetics are the real deal.
'11 Ram Quad Cab 4x4 SXT 5.7L HEMI (stock); 48,500m
'06 Pontiac G6 GT 3.5L 220hp; 64,000m
'12 Chrysler 200 Limited 3.6L 283hp; 28,000m
'99 Taurus 3.0L 2V Vulcan 145hp; 154,300m - Traded
Amsoil in all vehicles!