Update now at 225,000 miles and MPG average is at 18.5 after the hybrid battery change about 25k miles ago. Just changed the 12 volt battery uner the hood it had a AC Delco i think it was a PG48 or something 48 at 770 CCA that was 6 yrs and 4 months old by the date code so it gave good service. After doing some research I went with a Advance Auto parts AGM battery 760 CCA it was a perfect fit and with the fathers day 25% off discount was $149.00 Now the volts stay at 13 constantly I was seeing a lot of 14 15 volts readouts where the old battery was being charged heavily plus I was having some realy odd episodes where it would hesitate or have a crazy CEL pop up and then go away. Finally would not start one morning so out with the old and in with the new. I think what killed it was my front end alignment guy left the key switch on a few weeks back and pulled it all the way down completely dead. Only takes a few minutes to kill a battery in these if you leave the key switch in the on position, it apparently has a huge draw running the hybrid components. i still get complements all the time on how this ole TaHOe looks people like it. I am about as likely to drive it as my brand new Sierra Denali with 1000 miles on it LOL..........
