New aerodynamic designs allow vehicles to slice through the air unlike ever before. These designs have yielded measurable gains in fuel efficiency, manily due to greatly reduced wind resistance. However, the reduction in air flow underneath vehicles has created cooling problems for automatic transmissions. Pushed To Its Limits Petroleum ATF is dramatically affected by heat, which can ultimately cripple a transmission. Heat makes petroleum lubes oxidize, leading to a buildup of corrosive acids that eat away at transmission surfaces.
Heat also reduces the lubricating abilities of petroleum ATF, causing increased wear.
When this happens, the additives are no longer there to combat the effects that oxidation by-products have on the transmission and ATF performance. This means the service life of petroleum ATFs in today's engines is about 15,000 miles. High temperatures are only part of the problem. These transmissions have smaller ATF passageways and tighter clearances. If ATF gets too thick in cold weather, these transmissions will not function properly.