I purchased an 08 Tahoe hybrid with 79k miles about a 10 days ago and I am not getting the expected mileage. I am getting only about 14mpg in town. Everything seems to be working fine, auto stop works, and it not throwing any codes. It spends very little time in auto stop in the last few days. I was getting 18city/18hwy just in the last few days is has dropped to the 14. It has gotten blistering hot right now here in Texas 102-104 could it just be the heat and will get better?

 

A good thing to check is the metal screen on the HV battery. If lint has built up the HV battery will run hotter and knee-cap your ability to use the HV battery for storage/Re-Gen or depletion, GO power.

The key to fuel economy is storing/charging while stopping... then getting that energy back on the next acceleration.

Auto-Stop is OK in Stop and STOP and GO traffic.

 

Living in Arizona there are two things I have noticed the Hybrid doesn't like, 1. excessive ambient temperature(it was 117 here a few days ago) 2. Ethanol and/or MTBE laced Gasoline, which they add here for "Summer" gas.
When the ambient temperature here is 110+, my black tahoe can get over 150 degrees in the cabin(where the battery is) when parked in the sun. even in the garage the temps can reach 130+, it takes a looooong time to adequately "chill" the battery to make it function properly.
Ethanol kills the MPG as it is less volatile than gasoline and has less BTU's , the maximum ethanol blend is supposed to be 10% Ethanol/90% gasoline here in Arizona. However since ethanol is cheaper than gasoline and there is very little if any oversight, I strongly suspect many unscrupulous gas stations add more ethanol than they should. I have an acquaintance that drives a gasoline tanker and he alluded to this possibility without admitting anything.
During the winter I easily get 22-25 mpg, I'm getting 18-20 at this time.

 

Thanks for the replies! The truck is my wife's daily driver and she is rushing kids to and from all the events and is not as nerdy about mileage as me. I drove it for a couple hours on Saturday in mostly in town driving and was able to get 19.7mpg driving very conservatively. I have not checked the screen yet but I will for sure. And yes mine is black too and I have seen 157 interior temps before here. Interesting theory about the alcohol content i suppose I could try filling at different stations and monitoring it.

 

I find premium in top tier stations give good mileage.