I have a 2013 sahara unlimited and my old 2001 Aztec. I turned on the heat this morning as it was pretty cool this morning. The temperature gauge in the aztec wouldn't move until about 2 or 3 km. Then I would turn on the heat and the truck would start to warm up. This morning I was in the jeep and I was only about 1 km at most when the temp. gauge was moving. Man! I love that it heats up fast. Just one more thing I love about my new jeep.