what thermostat for my 05 4.8 5 speed? any hp gain, and when do stock fans come on?
 

What temp does the 05 4.8 5 speed fans come on? any benefit to a lower thermostat.

There was a lot of discussion about this a while back, and it's my "new" opinion that unless you're boosted, the lower t-stat won't do a hell of a lot for you. You might be able to squeak a little more timing out of it, but I doubt that you'd notice a difference. I'm running a 160* stat and I've been happy with it, but whenever I get around to building my LQ9 I'll probably go up to a 180* stat. The factory stat is 195* I believe. Not sure about the factory fan settings, but I know that it's over 200* when they come on.

From what I remember reading, the LS engines seem to perform the best and most efficiently between 180-200*

Mine are set at like 203-207 or so.

https://www.performancetrucks.net/fo...ght=thermostat ull find some good info here..

thanks guys i know lowering the thermostat kills MPG so I'll wait till i do the blower and revisit this

how does lowering the thermostat kill gas mileage?

The PCM is in a colder enrichment mode at lower temps, so running the engine cooler without tuning the PCM to compensate may have a negative affect on fuel economy. If the PCM is tuned accordingly though, fuel economy will not be affected.