Fuel Economy vs Temperature(above 105 deg)

I live in Houston, Texas, and it gets really hot and humid in the summer and due to the high humidity it is harder to cool things, and the older model Priuses didn't have any problems in this area. We normally start the day at about 85degrees and by mid afternoon we are at 98 with 100% humidity, and it's not raining.....don't know how, but that is what they say on the radio.

Atoyot

 

I'm generalizing here as I haven't had a nasty Texas summer day yet with my Prius. I would believe that the car's fuel efficiency would drop somewhat. Batteries in general like moderate temperatures, which is why they seem do do remarkably well in efficiency in sixty and seventy degree weather. When you start getting as hot as you are considering, battery efficiency will drop somewhat, and of course the running AC will also take it's toll.

 

This is my 1st posting so forgive me if I am rehashing already discussed topics. I live in CO and our weather varies greatly. So far I have been getting a relatively disappointing 40 MPGs. Thanks for the info on the gas tanks. I have filled (at the blinking bar) a low of approx 6 gallons to a high of approx 7 gaallons. Should we expect better MPG as the cars break in ?? Mine is 6 wks old with approx 700 miles on it.

 

Don't feel bad. I live in the foothills west of Golden and have been getting around 38 mpg and, yes, the tank fill varies from 6.5 gallons to 8.3 for me.

Regards

 

I live in San Antonio, and in the summer we usually are within 2 degrees of 100F each day. I know several Classic owners, who have had no problems at these high temps. The downside is that, on the Classic, the A/C compressor is run off the ICE, so gas mileage suffers because the ICE must run all the time if the A/C is on. (My friends report mileage in the mid-fourties during the summer with their Classic). And you don't want to drive around here in the summer without A/C!

On the '04, the A/C is electric, which should improve mileage during the hot months, although there will be some reduction due to the increased load on the traction battery (and, as a result, a bit more regen by the ICE). But I am hopeful that, once I actually get my '04, it will get significantly better mileage in the heat.

 

For those Prii running in the hot climates, whether dry or humid, be especially careful to consider the following to insure long battery life.

- Be especially careful to not block the powered vents with gear/bags/etc. that cool the main battery. The manual points this out (sorry/couldn’t find the page number to reference). The vent they mention in my 2005 manual is built into the right passenger seat, outside/top. I’m not sure if this is an intake or outtake vent……maybe someone can comment for I cannot find another vent. Blocking this vent can lead to possibly quick battery death in a hot climate. Battery technology has come a long way but the inevitable heat caused by quick cycling leads to heat problems and ends in premature failure if not controlled. It looks like the engineers have taken this all into account when they designed the Prius. Be especially careful of a passenger placing an item like a pillow over the vent to rest their head on.

- Another thing to consider….. Given that heat build up can damage the battery, then one might consider using their air conditioner most if not all the time. 70-80 degree F air blowing over your batteries is much more effective then 100 plus. I suspect the added cost and perhaps strain on the gas engine to run the air conditioner all the time to help maintain a cool environment for the battery may have a payoff for those who want to keep their cars for years. But then, this car is design so well I bet they even took that into consideration and perhaps the system can maintain acceptable ranges even for the Australian folks with air con off.

- By not interrupting the aerodynamicists when driving with windows open I wonder if the cost savings in MPG can be justified by gas consumption to run the air conditioner.

- But then…..what do I know. I now live in the Pacific NW USA with neither hot or cold extremes. I’m also a weenie and have grown so accustomed to 70ish degrees F that I run my air conditioner all the time. What I have noticed is that the “fogging up†effect frequently occurring on our windows in damp/cool climate is handled well by the Prius climate control if I leave it on “autoâ€.

 

I think I can speak to 105+ temps, although not much over, we rarely break 110 here in Tucson; our record is only 117. Perhaps someone from a really warm place (Lake Havasu City or Bullhead City), can chime in.

I've had my Prius over one summer, and the only real complaint is it is difficult for the AC to keep up with the amount of solar heating. Normally it takes on the order of 30-45 minutes to cool down to a comfortable 80 degrees, and by then I'm pretty much done with my commute. It's very difficult to get the inside temps to drop much lower than the high 70s.

Gas milage drops a couple of MPGs (right now I'm running ~55mpg, in our hottest month, June, the temps will be 100-105 most days, and I'll run ~50mpg).

Thanks,
Shawn

 

Well, whenever I go to St George, UT, I always fly into Las Vegas and take the St. George Shuttle van trip the rest of the way.

When the temps exceed 100 F, there really isn't a car or SUV out there that will chill you, even if you run it in Recirc. The solar gain is just too much.

All I can suggest, if it's legal in your jurisdiction, is to tint the windows.

The color of the vehicle makes a big difference too. In St George, UT, or Mesquite, NV you will rarely see a black or dark vehicle. Everything is about the same shade of white.

 

Our 2004 Prius managed just fine all of last summer in Las Vegas. The side and rear windows are tinted to the legal limit. The big problem is the windshield - my wife complains about the glare and solar gain. The car desperately needs a brow tint. With a heatshield in place, the car doesn't get much hotter than ambient when sitting in the sun - pretty amazing, considering temps of 160F and higher are reported in parked cars (usually after a tragic story of a child's death after being left in a parked car in the sun).

If the high ambient temps have any material effect on battery pack life, we won't know for a few years I suspect.

 

Tint it with Huper Optic 30 or 40 and you will be more comfortable and get better mileage. I'm working on an exemption to put Huper 60 on the windshield.