If you are concerned about overheating, you should purchase a ScanGuage II or similar product. The Prius only has a idiot light. Grill blocking causes the engine to heat up faster due to restricted air flow which in turn causes the engine to use less fuel due to the shorter warm up period.
It's not my thing, but I've heard that pipe insulation from a place like Lowes or HD works well. If you're not sure about the temperature, some people just block the lower grill. It's for DANG sure that you don't want to leave it there during the summer over there in the Lone Star State!!! Good Luck!
Here is a lengthy discussion on the topic. Good luck to you. First Morning with a Blocked Grill | PriusChat
Soft pipe insulation is used to cover the front grill opening in winter. Taken off in summer. Makes a significant difference regarding fuel economy and interior heating.
Let me tell you a little about grill blocking... Ive had my grill blocked all winter, since probably December. Yesterday I had to bring my Pri to the dealer for the recalls. I had to take the grill block out. I drove to work this morning with the grill un-blocked, temps in the low 20's. My average mpg's, which are an average over 320 miles on this tank of gas, went down a whole 2 mpg. I was at 46.8 and by the time I got to work (12 miles) it was down to 44.9. I was a little irritated needless to say! Long story short: I re-installed the grill block before I left for lunch. My avg mpg's were back up to 45.5 by the time I got home today. I know the OP was worried about overheating - I had a scan gauge and drove around with it connected all of the time. The only time I had a problem was one day when I went on a 4 hour highway trip at 75-80mph in 45 degree weather. The engine temps rose to 204f, no lights came on or no other indication of any problems. However, driving around in the city or short stints on the highway, the engine temps never went about 198f, which is fine. I just learned that whenever I plan on going to the cabin in Northern Michigan, I remove just 1 piece of grill block. That keeps my engine temps below 200f on the highway. I also use a block heater every morning on a timer set for 3 hours. That helps the Prius warm up quickly, the grill block helps it stay warm. Both are good for mpg's and I recommend both of them in combination for best results in the wintertime!
Hey PriusGuy 32, Are you blocking both the top and the bottom, or just the top? From what I have heard, the top is for the ICE on the Gen II and the bottom is for the inverter. IIRC, it is reversed on the Gen III. I have thought about blocking the top partially since I am a poor man and don't own the scanguage. I would like to try to eliminate some of the MPG drop off during the winter down here. Yes, we do have winter in Houston. Just not as bad as up there. Anyway, I appreciate your post's and was hoping for some input in reference to what I just asked.
Hey Thanks! I blocked both and yeah, I can see your concerns about an overheat especially being in Texas (right now, its 21.4 degrees outside and I think the high today is 28) lol. You dont necessarily have to use a scan gauge - if you have a smart phone with bluetooth, you can download, for free, the Torque app. Then go on ebay and buy an ELM327 bluetooth connector, they are like $20. The torque app will tell you everything that a scangauge will for much much less Partially blocking the top grill is a good start and will not lead to any overheat. I'd take it out once temperatures hit 80 or so, but a lot of Priuschatters leave the top grill block in year round. Ill be taking all of my grill block out once it gets hot if anything, but for A/C performance - the more air passing through the condensor, the better and Im a wimp when it comes to a/c in the summer
Thanks for the reply and info. I wish I had a smart phone, but that's another story. I remember all too well those cold temps. I come from the Buckeye state below you, so I have a good idea of what you are going through. At least you don't have to deal with the stupid hurricanes like we do down here.
Haha, yeah thanks for relating!! Maybe instead of grill blocking you should work on modding your Prius to be amphibious so that during the next hurricane, it will float out during any flooding without damaging it
Funny you should mention that. I did try to float a Nissan truck when tropical storm Allison came through here. It didn't do very well. I would not have been out in it, but was trying to get home from work. Needless to say, I didn't make it. And yeah, I know you are not supposed to drive in flooded streets. I am glad I am finally retired now. At least I don't have to drive every day now. If it is bad out there, I can stay home where it is high and dry.
