Synthetic

Gear oil lubricates your manual transmission and differential to keep the gears from making metal-on-metal contact. Some manufacturers specifically recommend synthetic gear oil, but it may also be an upgrade to the gear oil your vehicle was filled with from the factory. Your owner's manual will advise on the proper weight and type of gear oil to use. Common signs of low gear oil levels in a manual transmission include trouble shifting between gears and your transmission overheating, which may lead to further transmission problems. Low gear oil in your differential may cause whining or howling while driving. Replacing your synthetic gear oil can restore proper shifting and provide protection against wear and tear. O'Reilly Auto Parts offers gear oil, including synthetic gear oil, for use in most cars, trucks, and SUVs.