Maybe TBI 350's were harder on gas? Maybe smaller tanks in the older one? Both my 2000 and 2009 had 5.3's.Interesting. We had a 91 and a 94 and got in the upper 400's lower 500's with all hwy. We used to get upper 300's to mid 400's in the city. Ive been looking at getting a late 90's to mid-2000's suburban for the family.