Since dq is not yet awake, I will slip in my opinion. A perfect subject for the first major "differance of opinion" controversey of the new year. IMO , it takes a given amount of air-fuel mixture to perform a particular job. Example:: Imagine a car with 409-2 4s. Smooth acceleration from standing start to 50 mph. It doesnt matter which linkage is used, if rate of acceleration is the same, it would take the same amount of air-fuel . With progressive, you would be using much more of the rear carb. than the front, to acheive the job. With direct , you would use just enough of the primaries of each carb to perform the job. Remember, rate of acceleration must be the same. Why does direct linkage get poorer milage? It has nothing to do with the linkage, it has everything to do with the driver. The direct linkage has a quicker throttle response, low speed acceleration is quicker and crisper. That is the drivers choice!! You cant help yourself with direct linkage, to rap the gas pedal more when at an idle. You cant help accelerating quicker when doing the everyday driving. Its fun the way the car reacts with the two sets of primaries hooked together, at lower speeds. But if you could restrain yourself, and keep rate of acceleration the same as progressive set-up, then fuel milage would be the same, because, once again, it takes the same amount of fuel-air mixture to do the same job, no matter which linkage you use. So I guess my opinion is that technicallly , both types of linkage delver the same gas milage, but direct linkage has a bigger fuel usage factor, thus costing more at the pumps. Again , this is only an opinion, I have no tests, facts, or any data to support this opinion. Happy New Year to all!!!!!!!!