im a new member and new hybrid owner. I have had a 2008 base model w/ 3rd row seat Highlander Hybrid for 3 1/2 weeks now. The 1st week I averaged 27mpg in city and 26mpg highway. The next week I got 25/city and 23/highway. Now I am only getting 21-22mpg in the city. I've tried that mid level gas (tween reg and prem) w/o results. The mechanic at the dealership didn't have a clue. Anybody else doing this poorly. Any way to improve. Oh and our temps are 80+ degrees.

 

Your turned the A/C on..??

Now the ICE must provide HOT coolant for the HVAC's reheat/remix cycle after the A/C cools the airflow down to near freezing.

You can improve the efficiency of the A/C (and thereby FE) quite dramatically by running it in MAX COOL mode and then using the blower speed manually to regulate the cabin comfort level. It wouldn't hurt to purchase and install a water flow shutoff valve at Home Depot to stop the flow of HOT coolant to the heater core.

The ICE will still run occassionally to keep the coolant (and catalyst) hot but not as often with the shutoff closed.

 

Your A/C settings suggestion is appropriate for typical AC systems found on typical vehicles.

However, the Toyota Hybrid AC system is somewhat unconventional and more efficient than systems on conventional vehicles. The AC compressor is run by a computer controlled variable speed electric motor which runs at the most efficient speed to bring the evaporator coil up to the proper temperature for cooling and dehumidification (below the dew point) at the selected temperature and fan speed.

In a conventional A/C system, the A/C compressor is run off the engine by a fan belt so it's speed is controlled by the engine speed which is not at all ideal - low speed when sitting in sweltering traffic and high speed when it is not needed cruising at 70 miles per hour.


With the Hybrid A/C system, hot air from the heater core is not used indiscriminately and wastefully for modulating the air temperature as on a typical A/C system where the heater and A/C run at the same time for blending air temperature in the A/C mode.

Heat is only used in cases where the ambient air temperature is on the cool side and very humid. If left in auto under this cool and humid condition, the A/C will operate on a very low compressor speed and fan speed to get the evaporator below the dew point for moisture removal. However if this still cools the cabin air too much, a bit of heat from the heater core will be added to maintain cabin temperature.

Under these cooler conditions where you don't want this dehumidification feature, you can just turn off the A/C if you want to maximize efficiency over comfort.

 

Actually the lower level of airflow, s.l..o...w....e.....r moving airflow, through the evaporator resulting from the use of recirc and reheat/remix bypass will often result in a higher level of dehumidification than via the method you describe.

 

thanks. i'll try.

 

You will find lots of friendly advice all over this site; keep in mind that each person's experience with their HyHi is different, and what works for one person may not work for others. That said, I can offer my suggestions on what has worked for me:

- "Learn to drive like an old man." That means no sudden accelerations and sticking to the speed limit where possible. Driving a HyHi efficiently is going to require that you change your driving habits. Flip your display to show you the current MPG value, and watch how your driving style affects that graph. Over time, you will learn how to accelerate or coast to maintain 60-70MPH while maximizing MPG efficiency.

- As others have said, the A/C will have a negligible effect on your MPG. Driving with your windows open, however, can put a drag on your numbers.

- If you use your car for lots of short trips, you will lose efficiency. The engine needs to be warmed up sufficiently before it can start giving you the maximum return.

- Check your tire pressure. Make sure that you're at least at what the HiHy sticker tells you to be at.

- No need to use higher octane gas. That said, 89 or 93 should give you anywhere from a 3%-10% boost in MPH per tank, all other driving things being equal.

It will take more than a few weeks to figure out whether the problem is with the car or with your driving style. It took me over a year to be able to hit an average of 40MPG on my screen (it was there once for all of about 2 minutes, but I'll take what I can get)