[EcoCivic]

-I haven't had any luck with EOC for my driving style despite trying it several times. About the best it *might* have done for me over letting the engine idle while coasting was increase my tank average from 47 MPG to 48 MPG, but due to variances in weather, that 1 MPG gain isn't even directly attributable to EOC. For me, the possible tiny gain isn't worth the hassle, safety risks, extra wear on the engine and entire drivetrain from constant bump starting, etc, but YMMV.

I'd personally bock the grill as much as I can get away with plus a decent safety margin in the winter and not block it at all in the summer if you are using AC regardless of engine temps. I would think the decreased AC efficiency and longer compressor cycles from the condenser not cooling as efficiently has a good chance of negating any aerodynamic benefits and will cause unnecessary stress on the AC system. But if you won't be using AC, this part isn't a concern.

You don't want the fans running excessively from the grill block either, this will cut into your savings since the engine to fan motor efficiency will be ridiculously low due to the ~50% alternator efficiency and ~75% efficiency of the fan motors. Both fans together draw around 16 amps, which is ~224 watts. When factoring in alternator efficiency, running the fans is about an extra 2/3 HP of load on the engine.

The fans on these cars are no fun to change either, so I wouldn't take the extra wear on the fan motors too lightly.