Mileage penalty for Central Texas winter

that's not winter my friend, that's autumn. but you will probably see a 10% reduction. do you get winter blend?

 

if you don't get winter blend gas, you probably won't see much change. depends how much driving you do with the heat on.

 

I agree, winter??? however I would think you would actually do better since I would "hope" you would be using that A/C alot...

Don't forget, the compressor is on when front defrost is on....

 

Having been through two Central Texas "winters" with a 2010 Prius II, I have noticed that the MPG does decrease a small amount when temps are consistently below 50 degrees. Maybe 3-5 MPG reduction depending on temps, distance, road/weather conditions.

- Spindifferent

 

You might consider blocking 50% of your lower grill for the "winter" months. If you have a scan gauge, you can monitor the engine temps, but you should be fine (I've driven in 90+F with 50% grill block and my engine temps were still around 190 - 195F range, which is the normal, unblocked engine temperature).

The grill blocking will help with the initial warmup period, because it is limiting the cool morning air going into the engine (cooling down the coolant when the car is desperately trying to warm up the coolant). You may not see as much of a drop off in your winter MPG's by doing this.

If you have a scan gauge, you can also find out when you car exceeds the 159F mark (thus going into the S4 stage. This is when I, finally, turn on my heater and turn off my seat warmer.