[RedDevil]

Grill blocking won't quicken the heatup *by much*, but it will reduce fuel consumption slightly because of warmer intake air. But you need to monitor as hot intake air can have adverse effects.

Some cars that have EGR don't benefit much from a hot air intake. I only detach my snorkel when around or below freezing. Without my LGB the effect is almost nil.

(* edit. I meant to write that, just didn't. Obviously hotter intake air will heat up the engine more quickly, raising the intake temp even further. As Vekke has shown with a full grill block it is substantial. Actually the greatest heat source will be the exhaust system, and the quickest to heat up too. It all comes down to how much of the air that is heated this way will find its way into the intake.