While I gassed up once in a span of five weeks so far for the year 2013, the MPG rating at the last fill-up was as an abysmal 40.5 MPG (according to Fuelly; still, can't complain about gassing up once every 5+ weeks)! The reason is my commute distance has shrank from 20 miles to 4.7 miles and it's currently dead in the middle of winter. By the time the Prius engine heats up to nominal driving temperature through the internal combustion engine (ICE), I'm already half way done with my commute.
That means the Prius is in 100% gasoline mode during half of my daily commute to work, just to warm up the engine. I am employing grill blocking strategy to see if I can shorten the heating time to increase the MPG range back to the 50 MPG arena by blocking 67% of the lower grill,to start. Depending on the results I am seeing, I may increase the blockage to 90-100%. Why would this matter? Gassing up once every 5 weeks is one thing but gassing up once every 10+ weeks is a crowning achievement :).
For this trial run, I used a 1/2" x 6' tubular piping insulation purchased at Lowe's for $0.94 cents and can be found at the plumbing department. The insulation tube is then cut into fifteen 4.75" pieces and then slid into the lower radiator sub-assembly grille. I am only blocking the lower grille and leaving the upper inverter grille 100% wide open. Since my commute is so short, a ScanGauge II isn't necessary - although I intend to acquire one in the next coming weeks. If you plan on employing grille blocking strategy, I highly recommend investing in a ScanGauge II to keep tab on the coolant's temperature. I'll post an update on my next gas-up, which may be in 5+ weeks, for the results.
So far, with 67% of the lower grille blocked, I've seen a boost in MPG. Before, I was getting an average of 43.7 MPG. In the 4 day trial so far with grille blocking strategy employed, I've calculated the MPG increased by 5.5 for a total of 49.2 MPG. That's quite an increase for such a small mod. I'll increase the blockage to 90% next week and 100% the week following next week to see how the percentage of blockage affects total MPG.