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Electric fans are more efficient than mechanical ones as they are designed to move the most air at a set speed but a mechanical one has to work from idle to the red line which will compromise it's efficiency.


  • Engine warms up much faster and stays warm in cold weather.
  • Cools better at low RPM, when crawling, in hot weather.
  • Better power, better gas mileage. flex a lite advertises up to 18 hp and 2-3 mpg increases.
  • You can turn the fan off when going through deep water.
  • They are quieter.
  • They have longer bearing life.
  • If fan motor or wiring malfunctions you may overheat.
  • Deep water could cause the fan to short out if you don't turn it off.
  • Zip ties used to hold them can eat a hole right through your radiator...sort of a sawing action.
  • Stopping at a red light may cause the A/C to kick in and out.

XJ's need a CFM rating on 2000 or more
Source: Replacing the mechanical fan with an electrical

i have a flex a lite black majic on my Jeep Wrangler- and i highly recommend it. Mine is a 4 cyl Wrangler with the 6 cyl steel radiator- and i never have trouble overheating on this setup even in the hottest weather

Keeping your Jeep engine cool at says:
As for mechanical fans, both flex and clutch style fans can be less than effective.
While on the subject of fans, we have finally seen electric fans become strong enough to effectively cool an engine conversion. These are typically within the 2200 - 2800 CFM range. With some good fan choices on the aftermarket, some of the cooling difficulties once experienced with mechanical fans, are now lessened.

Hot under the Bonnet

Flex-a-lite Fans
  - 485 - High Performance alternative to the Wrangler O.E. Fan $240

last updated 14 Sept 2006