I would say up to 5 degrees I made these with ony .150" wall thickness for greater heat dissipation. I know other companies have there's rated at a 5 degree decrease in temps. But until I get a chance to to actually take a before and after temp measurement I can't really say for sure. I have just been so busy lately I haven't even had a chance to install one on my LT. Ps the temps have been cold around me. Hopefully by next weekend I can give an exact temp decrease.