The 750 4 x 4i had a bigger gas tank last year.
5.4 gal. verses 5 gal. in '08.
Not a big deal in some parts of the country. In these western states we can get a long ways from home.

I tried looking up part numbers to verify my suspicions, but can't seem to find an '08 parts fiche that wants to work.

What I think they did, is use a longer fuel tank baffle. (the white insert in the fill neck)
I wish I knew how long it was on my old quad but I never measured it. This one sure seems longer.
This would give it more room for expansion. Maybe less venting like some have experienced.

I filled the gas tank, then pulled the baffle and proceded to add gas untill it was aprox. 1" from the bottom of the main fill neck. I was able to add 7 tenths of a gallon extra.

Anyways, mine is 6". How long is yours?

The difference is b/c the fuel pump is now inside the gas tank on the '08 EFI 750, the other yrs the fuel pump was mounted on the outside of the gas tank.

SouthWest has it right, the fuel pump is inside the tank, thats the difference...

the FI should adjust fuel better for altitude changes and weather changes, you should be getting about the same out of an 08 on mileage as the older carb'd machines, maybe even better, i'll be analyzing mine, but seems to be getting around 17/18 mpg right now

Elkbow rides hard & fast all day & the mpg on his '08 is better than 16mpg on a avg on my '07.