I currently have mine on inside. was getting a lil wavy so i cut a new piece of cardboard and covered it with some vinyl flashing and zip tied it on. has anyone had gthere on inside and then moved to otside and noticed any difference?? i'm thnking that maybe on inside it might be catching air instead of pushing it around the car.
I think theoretically it would be better on the outside, but the difference is probably immeasurable.
Ditto - less stagnation on the outside, but given a small surface area - you're likely not to notice Then again, there's no one thing that makes a complex shape aerodynamic (other than a teardrop shape) - it's a combination of a lot of little (and likely subtle) things
Time is the best teacher. Unfortunately it kills all its students.
My solution is halfway between in front and behind.
I got a few lengths of foam pipe insulation from Lowe's or Home Depot. Inserted the foam in the grill slots.
Every third slot is only partially filled with foam to let some air in. When the weather warms up for real I'll experiment with adding or deleting foam from slots.
My grill has about 1/2 inch splaces between vertical grill slats (see avatar). I sealed the self-sealing slice in the foam insulation to make it a tube, then squished that flat and stuffed it into the slots. YMMV due to whatever width your grill slots and foam insulation are.
Currently getting +/- 50 mpg in fall weather. EPA is 31/39 so not too shabby. WAI, fuel cutoff switch, full belly pan, smooth wheel covers.