Back in early October, the Chicago Prius Group e-mail mentioned that Menard’s was having a sale on 1″ foam pipe insulation.  A topic on the PriusChat forum was linked.  The foam can be used to block the grille on the car.  Apparently blocking the grille will help improve fuel economy and heater functionality.  Blocking cold air from entering the engine compartment will keep the engine warmer, which means it will be less likely to run just to keep itself warm.  Also, keeping the engine warmer means you will get cabin heat sooner and maintain that heat.

So I picked up a package of the pipe insulation for a couple of bucks.  I had read through the entire topic on PriusChat and checked out pictures.  I sliced one of the tubes of foam insulation down the middle.  I then cut off the ends so they would fit the grille.  While pinching the foam half-tube, I would push it into my grille.  The foam would then expand while in the grille and the expansion and friction was supposed to keep the foam in place.  I did this for both sections of the top grille, above and below the silver splitter bar.  Later I would cut some slits in the foam so it could be pushed deeper into the grille opening.  I skipped buying some different foam to insert into the bottom grille opening.  It sounds like a pain in the ass to block and I am not that geeky about fuel economy or heat.  Also, without proper scanning tools, I cannot monitor engine temp.  In the dead of winter, I could get away with blocking both grille openings, but I am extra paranoid and want my engine and the motors and inverter to get at least some cooling.

Here’s a picture of the foam on initial installation.  Later I would push the foam deeper.

I put the foam in the grille when it looked like the temperature would be in the 40s or colder for a long time.  However, the temperature went into the 60s shortly after the grille blocking installation.  I kept the grille blocking in because I still had the lower opening clear.  I should also mention that on my third day of grille blocking, I lost the lower piece of foam that was in the grille opening.  It blew out of the grille while I was driving on Route 64 in West Chicago, going 50mph.  Fortunately no one was behind me to freak out about a long gray thing flying off my car.  I don’t know if the turbulence from the truck in front of me caused the foam to come out.  I was driving 55mph on the Elgin O’Hare the day after I installed the foam and it stayed put.

I haven’t bothered to replace the lower piece of foam.  I’m not sure I will.  The last couple of days had  temperatures around 25-35F, and my fuel economy is 50.1 mpg about 60 miles into this tank of gas.  I’d like to stay above 50 mpg this winter instead of dipping into the mid 40s like I did last year.  If I get bored or feel confident about properly fitting the foam into lower part of the top grille, I’ll replace the foam.