FYI, after owning this 9C1 LT1 Caprice for more than ten years, I can say that if you want factory behavior, get factory spec parts. Some parts are critical. I replaced my original thermostat with Duralast twice. I noticed that the gauge would give wide swings between 1/3 and 2/3 scale. In winter, the engine never warmed up unless I was sitting idling first with no air moving through the radiator. Then on the highway the engine would get so cold it would barely register on the first tick. The Duralast design has a little hole drilled in it which is not original design. I suspect it was allowing cold coolant to flow all the time. This winter it became intolerable so I installed an ACDelco 12TH10D. What a difference! The coolant now comes right up to temp whether I'm driving at highway speeds or sitting. The gauge goes right up to half scale and stays there unless I'm sitting. If I sit for more than a moment, the temp will creep up to 3/5 scale when the fan kicks on and the temp goes right back to center. Heat is good now even at 5F. These motors need to run hot for best fuel economy and low cylinder wear.