If you're looking for something to read Car and Driver tested the diesel Tahoe.
Where the six-cylinder Duramax shines is in its fuel efficiency. Based on current prices for fuel and diesel exhaust fluid—and assuming the EPA's combined estimates for rear-wheel-drive models of 18 mpg for the 5.3 and 23 mpg for the diesel—the Tahoe's Duramax option would pay for itself in about 80,000 miles. That break-even point is largely realistic, and it will shrink with the more miles spent on the interstate. We averaged 27 mpg on our 75-mph highway fuel-economy test, which is enough to give the diesel Tahoe a bladder-busting range of more than 600 miles. We haven't had the opportunity to test the highway legs of a Tahoe equipped with the 5.3-liter, but a GMC Yukon with the 6.2 got 20 mpg in the same test. Overall, our four-wheel-drive Chevy averaged 23 mpg.