You should not have to set the temp at 80 to get "hot" air. I have found the HVAC system on the 400h to be very good and pretty much "set it and forget it." I AM into turning the compressor off whenever possible (dry winter conditions and early spring/late fall) and ALWAYS for the last minute or so in the summer before parking the vehicle.
If you're new to hybrids and want to squeeze maximum MPG out of it, you will turn the HVAC OFF if conditions warrant. It's always interesting; if you pull up to a red light, the CAT converter is fully warmed up but the coolant still has to be warmed up to deliver heat and you have the HVAC set to heat the interior, when you push the "OFF" button, the engine will instantly shut off.
As far as the MPG readout, I have never checked mine using the "manual method." I think most owners say the readout is fairly close...certainly within 1 mpg.
I have 2008 Rx 400h; 131,000 miles sometime I notice it is blowing hot air while I set it to 70 and outside temp is 82 degree. Sometime it signals WATER TEMP. Lexus mechanic said may water pump problem and ask me pay almost $1800. Any suggestion.
I serious doubt it is a water pump problem. Probably has more to do with climate control servos that actuate the blend doors in the heating and cooling under the dash. As for Water temp, have never had that, but I would surely make sure that you are not loosing coolant from your radiator. If you are it could be a radiator leak or yes the water pump leaking but these would result in coolant level going down.
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