My thoughts exactly. Mtl and xl-18?
I don't think I would mix the two. The XL-18 was designed to compliment the QDC from Ford. Being that I'm no chemist, I don't think I would leave it to chance that mixing XL-18 with anything but QDC could lead to disastrous results. Even if there was a difference with the immediate results, who's to say that the XL-18 wouldn't cause premature breakdown in other fluids and cause increased wear within the tranny?
Arrest Me Red 2011 GT Premium
Six-pot Brembo upgrade; GT500 rear brake upgrade; Whiteline adjustable front and rear sway bars; Whiteline adjustable panhard bar; BMR rear LCAs and relocation brackets; Eibach Pro springs; Koni STR.T struts and shocks; Eibach cam bolts; Legato axle-backs; Forgestar Matte Black CF5s - 19x9/19x11; Michelin Pilot Sport A/S 3+