I have recently purchased my wife a 2002 Chevy Trailblazer LS (4.2L I-6). We love it, except for the fuel mileage. My questions are will a CAI (or stripped stock box) and a lower thermostat have a positive effect on both performance and fuel mileage (or at least the latter)?

I know what options there are for both, I just want to know if I have a good understanding of both of these upgrades in that they will positively affect mileage and performance.

Thanks!
Mike

They will both increase your gas milage. However, in the cold weather, a colder thermostat can sometimes have a negative effect on milage because the engine has trouble getting up to the optimum operating temps. At least that is how it is in my experience. I see you are from Florida though, so it shouldn't be a problem.

the 160* I had in my Bonneville did create problems, but I have no had any with the 180*. I am trying to find a Trailblazer/Chevy forum where the exact technical aspects of the engine are discussed in more detail in regards to these modifications.

CAI and get some exhaust work done Headers Hi flo cat and mufferlers will get you what your looking for

It'll help, but not much.
That'* the price you pay for driving a 5,000lb vehicle.

Gee thanks....

CAI and Thermostat it is...

Don't forget the exhaust, just got to get it to breathe better than stock

My parents own a 2004 Trailblazer with the same powerplant...with a KN filter and upgraded exhaust (hiflow cat, muffler) they saw about a 2-3mpg increase...not a whole lot but it does help.