The only time I've really noticed some power loss is trying to maintain interstate speed (ie 70mph) while going up big hills. Even then, it was a slight loss. Off the start, it feels the same as the worn out 285/75/16 that was replaced. The ride is really good on the road too. At slow speeds, I can feel a little more vibration, and it's just a tad louder, but it handles and rides really well. Especially for a mud tire.
I drove from Ft. Lewis to Portland today, and I got 13.76 mpg too. And that is calculated without taking into account the tire size. So, I'd questimate that the actually mileage is probably around 15 mpg.
I am kind of bummed now. The CEL came on. My buddy checked it and it's the EGR and O2 sensor. The AC wasn't blowing very cold, so I took it in to get the freon replaced and found out the belt was missing. So now I need to figure out if the pully is bad or if the belt just got worn and never got replaced, or maybe the bearing.
Oh well, in the grand scheme of things pretty minor stuff. I'll take care of the AC and replace all fluids next week. Then I need to figure out the EGR thing and replace the O2 sensors.
I see everyone buying parts from "CDAN". How do I get a hold of him to order parts?