RBurt,

May I ask what grade of oil and brand you are using in you TCH?

Thanks!

 

I use Mobil One full synthetic oil, zero-weight. I change oil and filter ever 5000 miles including, tire balance & rotation. The thin oil may help get 1 to 1.5 better mpg if your TCH is broke in.

I also use Chevron 86 octane gas with techron. I'm still using the oem Michelin Energy S8 tires with each aired to 40 psi cold.

 

One thing -- Yuma to Pheniox is a climb of about 1100 feet. That would explain the difference between the two tanks.

As far as the rest, high freeway speeds incur an increased FE penalty in very hot weather. This is becasue the temperature limiting controls for the traction battery limit the charge rate, and thus the number of assist states that are available over the trip segment. Additionally, the assist state current is also temp limited so less power is available from the traction motors during each power assist. When this condition exists, running the AC may have the effect of cooling the battery and actually increasing FE. I don't live in a hot climate and my experience with this is practically all in the California central valley, so I don't have any numbers, but I have experienced this operating condition.

RFB

 

I have considered this and wondered about dropping the rear seat to allow cooler cabin air into the trunk. Thankfully, it's seldom much over 92 degrees here in summer. If anybody has tried this, I'm sure I'm not alone in being interested in reading your results.

 

Toyota has designed the car to operate in who knows how high of temperature just as it is. The traction batteries are cooled from the cabin air when needed.

The 12-volt deep cycle battery in the trunk is good from -40°F to +140°F. This is the battery that powers the ECU and all lights including the dash.