Sorry to dig up this old thread but the topic is one that really annoyed me. I have been doing a lot of Avis renting in the US lately, and as a Candian preferred member always got charged in CAD at some poor rate.

Last week in IAD I took it up with an agent but after a long time typing away at his computer he finally told me that there was nothing he could do.

So I called Avis and eventually ended in their US billing department, where I spoke to a friendly lady who confirmed that she added my credit card number to the "exception list" - from now on, if I use this card to rent from Avis in the US, I'll be billed in USD. The lady mentioned that she had no influence over automatic conversions in other countries, and that I'd need to address those each time I rent.