gas mileage Mechanical vs Vacuum Secondaries

ramcharger said
Where in the world do you get your information?

I got my information from the sheet that came with my Quickfuel carb.

Here is the same information on Summit's website:

http://www.summitracing.com/parts/QFT-Q-650/

ramcharger said
If someone knows how to tune a holley style carb, a DP works great on the street with excellent manners.

You are correct. Mine runs great. But that's a big IF-most folks can't tune one of these to save their life. And if I wasn't racing, I wouldn't bother with it. And my fuel mileage would probably be better also.