Poor mpg

How long are your trips usually? How much highway vs city? I always lose a few MPG in the heat of the summer because I have to blast the AC and most of my trips are fairly short (under 10 miles).

Also, what do you mean by driving carefully? Sometimes babying it too much ends up giving you worse mileage. If you're trying to stay in EV mode with the AC blasting, you'll drain the battery pretty quick and force the engine to kick on and work double time to charge the battery and move the car. The car is set up to get good mileage driving it like its a regular car. While there are ways to drive it that are better, there are also things you can do that are worse.

 

If you're blasting the AC, it can have a big effect on the MPG.

 

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i think it's the heat. wait until things cool down before getting too concerned. in the meantime, start looking at all the other possibilities, especially the easy ones first like 12v, tyres and pressure, air filter, oil and etc.

 

^ Lotsa good advice and to-the-point questions above.

As an experiment, try driving without AC for a day, see what that does? Just leave the system completely off and run the windows down as much needed. At higher speeds you should be able to roll them up partially, recoup some aerodynamics.

If that's not gonna happen, due to 110F, I'd just be patient, try the experiment when the heat wave abates. Also, a few AC strategies:

1. Leave AC completely off for first few blocks.
2. Run AC on Auto, with temp set high, say initially around 80F. Aim for a temperature where the fan speed will fall back from full racing, say just to medium speed.
3. Gradually drop the temp as things stabilize and fan slows a bit, aim for around 72~75F as a final setting.

 

1. the fuel efficiency of a Prius depends on your top speed. If you want to drive a Prius at +80 mph on the desert flats of Arizona then you will probably get 30 to 40 mpg - which isn't too shabby for a eco speed racer. If you drive the Prius at 40 mph your MPG is more likely to be closer to 50 mpg.. which is why you need to identify the speed you are driving with your Prius.

2. A Prius fuel efficiency improves over increasing distance/time you drive it. Which is why you need to define the length of your daily commute.
If I drive my 2010 Prius for under 1 mile and 3 minutes - I'm lucky to get 22 mpg - sometimes I get 12 mpg.
If I drive my 2010 Prius over 7 miles/ 30 minutes my 2010 Prius fuel efficiency jumps to about 45 to 50 mpg most of the time.
The exception to this rule is if you have a plug in Prius and you recharger her every night OR you heat up your Prius ICE with an engine block heater OR if the driver hypermiles ....

3. A Prius fuel efficiency depends on the tires it is using and if the tires are properly inflated. A Prius needs to be fitted with special low rolling resistance tires - like Goodyear Assurance Max Fuel or Michelin Energy Saver All Seasons or Bridgstone Ecopia Series. Check the type of tire you have and make sure the tire pressure. is good. If the tire pressure is low - pump it back up. If your previously owned Prius came with crummy tires - replace them.

For buyers of a used vehicles I always recommend having a competent mechanic check it before you purchase it - find a competent hybrid mechanic in your area might be problematic so you might want to have a Toyota dealership check out the hybrid system for you - note also that Arizona is no longer a CARB State - so at 111.000 miles a Prius hybrid system warranty is over- if the hybrid system is failing - the hybrid is in RDDD.

For drivers in very hot climates - keep the cabin temperature under 85 degrees Fahrenheit - making double sure the battery cooling intake air vent is clear. Keeping your HV battery cool will help it perform optimally.

 

50 mpg and above is certainly available.

In addition to what others have said, what brand and model of tires are on the car?

 

I recently discovered that extreme temperatures cause low mpg regardless how you drive or how you use AC.
If you don't use AC, the battery gets over heated and the computer will protect it by disabling the regen braking. Without regen braking, your mpg drops around 5pm to 10 mpg. If you blast the AC to cool the cabin temperature to cool the battery, you'll get your regen braking back but ac drops 5 to 10 mpg. It's catch 22.

 

Try sensible moderation, somewhere between OFF and "blasting."

 

Interesting, we have found that not to be the case, but I guess YMMV.

 

If you don't blast the AC, cabin won't cool down. You'll get hit double with AC on and no regen braking. The loss of regen is only temporary and will recover as long as there's enough cool air circulating in the cabin to get sucked into the battery cooling vent. The first few minutes of driving is the worst. Once the cabin is some what cooled, you can back down the AC. Even then you're AC is still drawing nearly 10 amps even in ECO mode when stopped. On my way home from work (exact same time, exact same traffic), I've driven in different temperatures from 75f to 110f I get 60-65mpg at 75f and 42-46mpg at 110 with AC at coldest and 6 bars. Any lower fan speed, the interior begins to heat up and I'll lose regen braking. I got lower mileage in the summer time than in winter time at 35-45f low. In winter I can always get at least 52mpg. In the summer, it's always high 40's. Can you get mid 50's at 110f? sure, if you want to die by heat stroke and piss off everybody behind you.
BTW, there's nothing wrong with my battery cooling fan. I just cleaned it 2 months ago and it looks almost brand new. There's no obstruction in the vents. The cooling fan ran at its highest speed during cool down.

 

Havent had to much change so far this summer but in the winter time having my heat blasting all the time extremly impacted my MPG som days only getting 35 over a 30 min drive or longer