[THEFERMANATOR]

Originally Posted by phatdaddy

probably right ferm. i'm an old man and drive like it. i like the fuel mileage of the the 5.3 vs the 6.0. probably put 15000 miles a year 0n it with 14500 non towing.

if i had it to do over, i;d look at suburban/yukon xl. absolutely no room behind third seat

The 5.3l and 6.0l have been proven to get almost identical milage when setup the same. Most who have swapped out the 5.3's for 6.0's, haven't hardly seen a change in mpg. The big differences between a 2500hd with a 6.0l and your tahoe with a 5.3l is trans gearing, torque converter stall, rear end gears, and shift strategy. The 1500 tahoe is setup primarily for mpg, many had 3.42 gears, a low stall torque converter, a REALLY deep 1st gear with huge rpm drops between the shifts, and tuning setup to keep the rpm's down to furthur optimize milage. All 2500hd, 3500, and many 1500hd's with the 6.0l had 4.10 gears, they all had the 4l80e trans geared for optimal towing, a LOOSE converter to keep the rpm's up, tuning that is setup to hold the shifts out even driving easy, and the torque converter is basically on or off, not varied like the 1500's to keep rpm's down as much as possible at all times. Put a tune in your 5.3l, and it would be a completely different animal towing.