Donít use green antifreeze and must quality red/orange antifreeze will work just fine (see below). I agree with
, changing the thermostat might not make much of a difference on a mainly street driven car. If you drain the coolant or do a coolant flush, make sure to follow the procedure in the service manual so you donít end up with air pockets in the cooling system. Do you know when the brake fluid was last changed/flushed in your car? I know that most people don't realize that Lotus recommends changing it once a year, which is probably over-kill for most cars but brake fluid is hydrophilic and can cause corrosion in the system.
TL/TR: Regular (green) antifreeze is composed of water mixed with methanol and ethylene glycol. Red/Orange antifreeze (sometimes generically called DEX-COOL which is GM's name for it), as well as other organic acid antifreeze, are not glycol-based. Instead, DEX-COOL is created out of a combination of different phosphates and silicates as well as the organic acid technology (OAT). What you are looking for is antifreeze that says it contains organic acid technology (OAT), conventional antifreeze doesnít use OAT, and most car manufacturers use the same OAT specification when they specify their coolant requirements.
2005 Ardent Red Elise, Gut Sport wing & splitter, custom diffuser, Sector111: DSBrace, gPan3, subStuffy2, Larini Sport muffler, decat pipe, Schroth Racing 5 pts, wheel studs, Team Dynamics 1.2 with Hoosier A6s, Koldflash 200 ECU flash, BOE rear clam hinge, BC Racing single adjustables, Hawk pads, SS Brake Lines, HID lights, custom tail and high mount brake light...and much more...