air conditioning and mileage

What is your general mpg loss in very hot weather with air running? Anybody have any tips re airconditioning use? Thx.

In an effort to see just what mpg you get while leaving the car on "automatic," (meaning the lights are automatically on, the a/c is automatically on) I have driven this way for nearly 5 months. Mpg per tank runs 33-39. I cannot get a full tank to go over 40 mpg.

I do mostly city driving in New Orleans, where it is hot 9-10 months of the year. I did check the tires and get them up to factory levels.

What are the factory levels? Prius owners in the groups and john1701a.com suggest 42/40 psi for your tires.

Quote, "42/40 PSI (2.9/2.8 bar) is what many Prius owners recommend for optimum performance. For maximum performance, use a pressure of 44 PSI (3.0 bar). Whatever you decide, just remember that low pressure results in lower MPG drop and a shorter tire life. "

pkastl: I live in Houston so I imagine the weather is similar to that of New Orleans... I get about the same MPG as you do (38-42).

I've noticed an impact on mileage when A/C is on, and the mileage is worse when the A/C is playing catch-up after first starting the car when the sun has heated the interior. Here's what I do:

1. For the first few minutes of driving, leave A/C off and windows wide open, fan blasting.

2. If running an errand, put the car in park instead of off, remove the physical key from the fob, and lock the doors manually with the key. Increase A/C temp a few degrees so that A/C doesn't have to work so hard when the car is just sitting, but interior will not super-heat. Turn off the headlights while the car is parked.

3. Use A/C on automatic mode if you will be driving for more than 15 minutes or so. For shorter trips, use manual. (On auto, the A/C will crank for a while to cool the interior then gradually back off).

4. I would be careful not to overfill tires. Use maximum PSI recommended by manufacturer, but going over that, while it may improve milage, it will increase tire wear and wear on other suspension components.

My 89 2.0l auto 4cyl Camry is obviously not a hybrid but for information purposes, AC decreases highway mileage by 4 mpg(recirc mode) and this has been seen many times on trips.MPG goes from 40 mpg(60-65mph) to 36 mpg.

[QUOTE=woofhaven]
1. For the first few minutes of driving, leave A/C off and windows wide open, fan blasting.

I'm so confused over the "climate control". It seems that if I turn the a/c "off" there is no fan assist. If I turn the fan on, the a/c seems to come on to meet the temperature setpoint. How can you get purely "manual" operation?

I'm so confused over the "climate control". It seems that if I turn the a/c "off" there is no fan assist. If I turn the fan on, the a/c seems to come on to meet the temperature setpoint. How can you get purely "manual" operation?

All you need to do is select "Climate" on the multi-function display, then hit the "A/C" button in the upper left hand corner, to deselect it. You then hit one of the fan speed buttons to manually operate the fan.

All you need to do is select "Climate" on the multi-function display, then hit the "A/C" button in the upper left hand corner, to deselect it. You then hit one of the fan speed buttons to manually operate the fan.

Thank you, I have a new Prius and could not figure this out either.
JT