I think the one thing you all are missing is detonation. The reason i try to keep my motor cooler is to fight off detonation. With my 160 ts i can run 87 octane on cool days. But i keep the temp at 160 with an adjustable fan thermastat. If your motor is stock you won't detonate especialy if its FI so I would change the fan turn on points first then decide if you need to be cooler. We advanced the hell outta my buds tbi car, bout 8 degrees, and it started detonating on the top end and on cruise. He swapped in a 160 thermastat and it got rid of some detonation. We checked it with a scaning software. Just look at the big picture of how all the different parts of your motor works together.

 

LOL Beefy

Ed Maher, sorry for all the flaming. Bad week I would say. Anyhow, my car does seem to do things quite a bit different than what "should be" happening. I understand heat range of spark plugs and you are absolutely correct that cold plugs foul quicker and hot plugs foul less easily in more fouling conditions. However, in MY car, it's completely opposite. I never have understood it. My car is driven 80 miles round trip to work Monday-Friday and I can't get the hot plugs to last as long as the cold ones. In regards to that, I recently read that hotter plug do foul less easily but for higher performance engines, not stock, the colder plug is the best way to go with more performance due to more cylinder pressure, especially with high perf. engines having higher compression than stock and colder plugs in high perf engines may actually foul less easily depending on other conditions. Maybe that's why my car does it. *shrugs*

To end all arguements I'll just simply say use whatever thermostat you feel comfortable using. I personally think the 160 vs 180 arguement is actually about as pointless as the MAF vs SD arguement because no one will ever agree and it will always be approx split down the middle on which side to take.