X-One tires

I wouldn't buy an 08 for half the price. The 08 cats are failing at unbelievable rates and the cummins aint exactly great. but if you have to have an 08 I'd make sure it isn't a cat. and I hate to say that as I've always loved cats.
You'd be best served by buying an 05 or 06 and running it untill they get all the problems ironed out with these new emission motors.

I'm not going to guess at your mileage

The X-1's are running about .4mpg better than duals but they are not lasting as long so you are looking at a wash from what most are saying. I don't run them but eskimo or beargator could give you better info as they run them.

some guys love em, some hate em. same for reports of snow handling.

they are lighter though which if you are running heavy there is a benifit there. The only way I really see them being worth the investment in shorter then three years is if you can get them spec'd on the truck new

 

If you have them on both truck and trailer, you can expect between .4-.6 increase in mpg depending on what tires you are comparing them to. There is a huge difference between the most fuel efficient duals(Michelin steers in all positions)and the least efficient duals(heavy luggers in drive position). That difference can be as much as .5 alone. So if you go from a heavy lugger on the drives to a super single with a trailer tread on the drives, you may gain as much as .6-.8. My drivers don't really care for the handling characteristics of the singles(they all said they feel "skaty and unstable), therefor I'm not going to buy any more of them once the ones I currently have get replaced. Medman is correct when he says that the tread life just doesn't seem to be what one would hope(at least not in my personal experience). We get much better life out of the xda2+ energy drive tires that we run(duals), and if you are only talking about putting them on a tractor, the difference in mileage between an X1 and xda2+ energys is about .2-.3. The difference between running x1 drives and running xza3(steer tires) on the drives is only .1-.2 at best. I know this may seem like information overload, but you asked for it.lol

 

Friend of mine has Prostar with ISX500,3.73 rears ,13 speed manual and hauling stepdeck from coast to coast.Current MPG is 5.75.

 

I agree so buy an older truck with a more fuel efficient engine, anything newer than 04-05 is going to cost you more in fuel, and I wouldn't buy a cat newer than an 03. Also don't forget about cleaning the diapers in the exhaust on those emmision motors, and also the fact that the new engines run soooooo much hotter that nothing will last anywhere close to as long as the old stuff

 

there is a reason they are giving away the new trucks. go look hom many are sitting on the lots and how many used 08's with under 100k on them.