Originally Posted by Schweden

I once did not include LDW in my reservation and later added it on at the time of rental. Looking at the receipt, the charge for "min. Selbstbehalt LDW" (min. excess LDW) was the same at 117.67 Euros for the week. However, the rental had a large extra charge of 138.18 Euros for "Vollkasko- und Diebstahlschutz" (full comprehensive and theft protection). All my other rentals where I added full LDW online did not have this charge. However, rates for that week were high so I'm not sure if I was overcharged as the difference couldn't have been more than 50 Euros. Perhaps the system just added this charge as the base rate indicates that it was a promo rate. In any case, I recommend getting full LDW online first so you get a better price estimate and as adding LDW later won't be cheaper.

In my experience, they usually let you pick whichever vehicle in the class is available. For example, I was offered a C220, 320d, or A4 on an FDAR reservation. However, non-airport locations probably only have 1 LDAR vehicle available so you might be stuck with an A6 or something.