Sorry to run this by everyone again. About blocking the grill for mileage in winter. The caveat seems to be a chance of overheating the engine if outside ambient temps are too high and your Prius is not equipped with Scangauge, or whatever. Wouldn't standard Prius instrumentation give you a dashboard warning light so that you could pull over and remove a few of the foam inserts before you fried your engine? Someone pointed out that enough air comes in from underneath the bumper to prevent the engine from getting seriously overheated in most circumstances. Comments I've been using full blockage for a week or so, and afternoon temps are around 50-55F, but gradually getting colder. Have noticed an improvement in mileage and a very quick time interval from startup to max efficiency. Bob
If you overheat you'll get a light...but it's better to avoid getting to that condition in the first place. In any case, I've not heard of anyone get to an overheat situation at any temp below 60 under any conditions.
Being a pants & suspenders kind of girl, I only plug the upper grill. Mileage is better, overheating worries non-existent. I don't have a high risk tolerance. Having said that, ScanGauge is on order. . . .
Bob: i wouldnt worry about it a whole lot as long as temps are 55 F or lower. i block the entire grill and i havent had problems. i will only occasionally see water hitting 204F.... highest i have ever seen was probably 206 or 207. done a trip from Portland to Everett with 5 people in the car on a day that was in the low 50's and didnt have an issue at all.
