I couldn't find the main thread about grill blocking. Today I discovered I can drive 70mph in 60F weather and be fine. I assume my thermostat was opening. Was only a 20 minute drive and only 10~ of that was at 70mph. I also have oversized AT tires and a 1.5" lift, so extra drag/load. But yeah, I have the bottom grill fully blocked off. I used 1/2" ID pipe insulation. Had the half cut seam thing. Cut it all the way and then pinched it inbetween each fin space in the grill. I think it was 25" and you need 2 of them. The ends kinda point inwards and that's what secures them. It was putting off heat like never before. Been having some 30-40F mornings and it just struggles. About a 20 minute one way to work. 7 miles, lots of stop lights and such, top speed about 45-50mph. Engine struggles to put out any heat. Even started to drive in B mode because it kept turning off the engine at lights that would only get to 130F water temp. Would turn back on at 120F~ anyways. About 5 minutes into my drive, at 30-40F, it starts to put out some slightly warm air. But by the end of my drive, it still hasn't warmed up the whole car enough to be comfortable. Just wanted to share.
