Low coolant temperature will hit your fuel economy. AFAIK the gear shifting is based only on transmission temperature so your failed thermostat shouldn't affect this.
phum wrote:
What are the problems with the inline fix?
It's far from conclusive but there have been some overheating issues, blown gaskets, warped heads etc that
may be correlated to the use of an inline thermostat.
Cheap - Personally I've modified four housings as per the Sargeindustries design - for myself, a local buddy and a couple of LOST members. If you have access to a machine shop and some time and the necessary skills it costs a few bucks in aluminum plus the thermostat.
Easy - If you can't do the above mod the manufacturer part probably most closely meets your requirements and regardless what anyone tries to tell you around here there's really nothing wrong with the OE thermostat other than the fact you'll probably be replacing it again in a few years if you still own the vehicle.