Hi JazDale
RE your questions
Yes there was a definite improvement in the quantity of LOFs in the shop that was attributed to the card. (it took about 6 months too really see the change) . One of the key customers we gained was the young crowd that often went to a local jobber (too save money with a low cost lube oil filter). What we found happened is mom or dad loaned [sometimes by free will

] their son or daughter the prepaid card to come to our dealership. In this case it usually is an older vehicle that required some tune up or various things too be completed. By default CP did increase.
The thing is no matter how good a program or sales incentive it still comes down to people to make it successful. Its important that the dealership staff (shop and office) buys in to any marketing concept else all is moot.
As far as handling money, accounting set up a separate account for the monies collected. Service set up a special RO code to handle the internal billing.
This was a prepaid service. All taxes paid at time of sale.
The accounts receivable / payable clerk also kept a manual list just in case and kept track of the usage of each customers card. This was done in case a customer told us they forgot the card. She could instantly tell service if the customer was on the list and how many oil changes where left.
It does take a bit of cooperation to assure the success of the program. Once everyone had his or her procedures and accounts set up, the concept worked very well.
Often the various internal departments work as islands on separate sales promotions. The neat thing is that this small LOF card tied parts, sales and service and accounting into a combined marketing program. That in it self was a positive aspect for the dealership.