I'm interested in this additive, but a little confused about the dates involved. Deysha said that the change to XT-11-QDC happened on 8/15/11, but my '12 GT was built on 6/27/11, so it still has whatever fluid came before that. Am I ok adding the XL-18 to it, or do I have to drain and fill with XT-11-QDC first?
Adding only the XL18 to your old fluid will be a waste of money and time.
You will see far more improvement by changing the trans
fluid to QDC. Then the XL18 will improve on that a little.
I changed the fluid in my 12 GT after driving the car for nearly 2 years and it almost eliminated the 2 gear roughness, a month or so later I added the XL18 and I haven't had any 2 gear roughness since.
2012 GT Prem. Black, 6MT82, Brembo Package, Rear Sensing Security Package, Appearance Package #5 ,3.73 LS Axle, GT500 Axle Backs, MGW Shifter, FRPP Tune.