Recently went through this exact situation.
Ordered a new car for my wife 6 months ago... To be fair, the dealer was upfront then about mandatory finance for 6 months, but I thought "we'll see in a few months" (when the car was supposed to arrive)...
When the car arrived, I spoke to the NCM and finance manager and they maintained the financing was mandatory, but quickly offered an upfront rebate for the interest for the 6 months. For the aggravation, I also managed to squeeze a little extra out on the trade and drove away with a new car and a cheque... And yes, I marth'd my way through the finance calcs to make sure I wasn't leaving any money on the table.