Hello from Dallas, the new surface of the sun where we have had 60 plus days of 100+ degree heat.

I have enjoyed my 2009 Tahoe (36K miles) very much, but disappointed of late as my mileage has gone to 12-13 in the city. I don't hot rod, very conservative driver. The only change I have made is putting new set of Nitto Crosstek http://www.nittocrosstek.com/ tires on it about a month ago. They look good, but I am wondering if they are causing the issue, besides the heat.

I have not had the throttle body cleaned, but headed to Sewell GMC today for that.

Curious if anyone else has seen lousy gas mileage in a super hot climate this summer.

Thanks in advance, Paul

 

My (somewhat novice) understanding of the hybrid system is that the performance can degradate if the hybrid battery gets too hot or too cold. If your cabin temperature is at a comfortable level (i.e. you are running the A/C) and if the vents to the hybrid are clean and open and the air flows across the batteries, the outside temperature should not have such a pronounced effect on the MPG performance as you describe.

I'm sure one of the experts will correct what I have wrong here.

 

Rolling resistance on the new tires is the same as the old ones?

All hybrids have this low Rolling resistance tires to make the high mileage combo.

If your tires are below 420 Thread wear, and you add some super hot surface that makes them glue to the asphalt/concrete, you have there your low mpg numbers.

Probably. just my 2 cents

 

From my experince, HOt weather does affect the mileage specially in the city driving, where the battery doesn't have enough juice, and forces the engine to keep on running.
plus the performance of the battery itself deteriorates in hot and cold weather as well, which doesn't help much.I don't get more than 16-17 MPG on mine, i live in a hilly city, where you hardly find flat roads, I compensate hat when I go outside the city on weekends. hope this helps

 

It has been extraordinarily hot this summer in Phoenix(I think we had 30+ days of 110+) and my mileage has gone down significantly, I am getting 18-19 mpg where I was getting 22-25 mpg this past winter. I think the summer blend gas we use here in phoenix has something to do with it too, they raise the ethanol percentage and add something called MTBE to gasoline during the summers here, it's suppose to help with smog but it definitely lowers MPG on all cars.

 

Hey Paul, I am in Dallas as well and have a 09 Yukon hybrid. I was seeing similar issues, where the mpg dropped to 13.5 from 17-18, also the vehicle once just stopped and lost all power. I took it to the dealership and had a detailed conversation with the technician. Per him, the hybrid battery has 7 temperature sensors. The battery gets cooled from a vent that goes from within the car and unless the temperature is less than 137 the battery is out of the picture. The charging starts once the temperature is less than 137. In my case my drive is 7-8 miles one way, so the temperature of the car interior did go down by the time I reached home, but the battery never got enough time to cool down. The dealership kept my car for 2 days where the tech made the hybrid part go through a learning phase and made some minor adjustments to the programming as to when the battery should kick in. So far my mpg has gone up to 16.5. I hope this helps.

 

My Tahoe has done very well this summer even though we had record temperatures that beat history all the way back to the 1936 dust bowl days. My truck has done very well as long as I start the vehicle with the doors open, and the air-conditioning on full blast. I am still getting fantastic 22 miles per gallon on the highway at 70mph, and even better putting around the city at 30mph or less. The battery seems to like the high temp as long as the interior air-conditioning is on. I always run it because I am disabled and couldn't do without it. High heat is a detriment to my safety. I've had all factory reprogramming call outs. My truck is still low mileage - about 5200 miles. It is a 2008, so my programming may be different, but physically I can't tell the difference between years. I'm sure there probably is, though.

 

P.S. - I have the original factory Continental tires, and the heat has been triple digits all summer without let up until now. Temperatures consistently 104 F to 106 F and higher. I'm using the cheap regular gas.