Why "almost" 2 qts? At 1.89L, a full 2 qts is the minimum I'd put in... you say "to each their own" but if the IB5 takes 2.1L I just don't see how an additional gear added with an IB6, assuming same internal capacity, would take it down to only 1.67L as in the manual... only 1.5L came out of mine at 12k, that is ridiculously and dangerously low to me, a new car shouldn't have so much whining and grinding. I actual had minimal "clunk", so that wasn't enough to even bother to try to get warranty for the half shaft TSB, where after repair they are instructed to add 2L. So doing a full 2L of Ravenol (BG Synchro looks great too) REALLY helped a lot and made my trans how it should have been new... I know if I kept driving it with the only 1.5L I would have certainly damaged the trans over time... Anyway, I think you should be fine, just wanted to add my experience in using 2L and how Ford uses that much after a warranty repair too...