I've been checking out prepaid maintenance plans, and they work out a bit cheaper than if you were to pay for them at the required interval. But comparing the prepaid and regular service schedule for instance, the prepaid plan has timing belt replacement scheduled at 100,000 km (62,500 miles), whereas it is 60,000 km (37,500 miles) with the regular plan. I couldn't help but wonder...are cheaper parts generally used for prepaid maintenance, or do they skimp/postpone replacement of certain items, etc. to reduce costs and make them more attractive? Obviously it changes from manufacturer to manufacture, dealer to dealer, and in this case country to country...but I was interested in a general insight so to speak.