I worked as a mechanic for many years. Many Nissan and Infiniti vehicles use a rubber timing belt to keep the camshafts running correctly with the engine. These cars will run for 300,000 miles easily if kept maintained. The problem is the timing belt wears out. Nissan/Infiniti recommend changing the timing belts every 90,000 miles. Normally the belt is under $40 by itself and labor is a few hours. You would be looking at a $300 bill to change the belt, before it breaks, as a scheduled maintenance item. The problem is when people don't change the belt. After all, the car runs, why spend money on a car that isn't broken? But wait. If the belt breaks while the engine is running, the engine's parts go out of sequence. The pistons will actually hit the valves, causing expensive internal engine damage. It is not uncommon to find the cylinder head has to be rebuilt due to bent valves. Sometimes cracked pistons need replaced, meaning a whole new rebuilt motor. What would have been a $300 maintenance job is now a $2000 engine rebuild. Why is this important? When buying a used Nissan or Infiniti with over 100,000 miles, the first question asked should be, when was the timing belt changed? Do you have receipts? If the owner can't prove the belt was changed recently, if you decide to by the car, be aware you will need to get the belt changed as soon as possible to prevent ruining the engine. A deduction in price can usually be negotiated to partially offset this. EVEN IF the owner swears up and down the belt was just changed, but he lost the receipt, get the car checked out by a reputable shop to confirm this. Call the shop who supposedly did the repair and see if they have a record of it. If not, get it done yourself- You don't want to suddenly be receiving a $2000 repair bill plus towing! Good luck on your purchase, and if this was helpful to you, please indicate it below.