i just purchased my xf so i haven't treated the rubber yet. but i used to own a '95 corvette and used gm's dielectric grease to lubricate the seals. it worked pretty well though it can be a little messy. you can just put alittle on a towel, diaper, etc. and rub it on. the corvette had very soft rubber to minimize leakage into the targa top and doors and it was extremely prone to cracking. as a matter of fact, i was fortunate to get all mine replaced just before the warranty expired just a week after i purchased it used. the rubber can be quite expensive. i'm not sure how the xf's seals will last. i haven't read that far into the manual yet to see if there are any recommendations. so, i will eventually try the grease on the xf. hopefully, others will chime in here and can help determine whether my recommendation makes sense for the xf.