My C240 warms up on cold days (10 degrees) after 15 or so minutes of driving. I suspected a faulty thermostat, so I replaced (used Wahler 87 degreee unit purchased from MB dealer) and noticed no changes in slow warmup. The car is manual transmission and I usually coast when going downhill. I also don't idle when first start the car and immediately drive it.
What seems to be causing the slow warmup??