I believe I know what's causing my high fuel consumption.
I think I have a lazy thermostat. It's not stuck open, I have no codes with GT1. But, I know, this car should heat up pretty quick, which it does not.
Now, with cooler ambient temps, I noticed it took forever for the needle to go to the 12 o'clock mark. I also noticed that the instant mpg goes down drastically until the needle starts to stabilize, then the instant mpg is what it should be.
For the last few days, i did the KTMP test after cold starting (ambient temps around -12°C to -14°C). So, here is what I noticed: the temp climbs nice and steady antil reaches the 55°C to 60°C mark. At this point, it takes forever to get to 94°C. In distance: it takes about 300 to 400m (yards) to get to 55°C, then another 4 Km or 5 Km to reach 92°C to 94°C. The needle stabilizes at 12 o'clock around 72°C.
I think that while the GT1 does not show a failed thermostat, the bloody thing opens way to early at the 55°C to 60°C mark, instead of the 94°C mark.
My commute is about 12 Km one way, so with colder ambient temps, it's no wonder that now my mpg is even worse. As I said, the GT1 didn't find a single issue with my car, which is strange the way the t-stat is acting up. I remeber having the needle at 12 o'clock very soon after starting the car stone cold, which is not the case now.
Anyone else experienced this? My t-stat is a dealer OEM changed October 2010.