Carb. Mechanical or vacuum secondaries?

And frequently using the secondaries is my point exactly regarding fuel economy with the DP.
My thought is if somebody is conserving fuel, then they are not flooring it. Like going back and forth to work per say. The DP will do all as well on the front primaries as the VS. IF a guy is hot rodding, flooring it, burning tires, then gas mileage is NOT on his mind so the DP will give better performance and mpg is not a concern during these activities