My 7 year old OEM battery was functioning just fine when I decided to install my Ford Racing headers last week. When I removed the trunk tray to disconnect the battery, I noticed the battery had started to leak near the terminals and battery acid was pooling on the top. It was just by sheer coincidence that I discovered this before it did any damage. The OEM batteries are now 7-8 years old and should be inspected/replaced even if they are working.