I have an A15 in my B310 running an A12 carb. Performance is still very good, but now I have an option to get a downdraft Weber 32/36 for a good price but I was wondering how big an effect it would have on my fuel economy. I know they aren't as bad as sidedrafts but will it drink gas under normal city and highway driving or only when I flat my foot?

I have a sentra with an E-16.I put a 32/36 on it and my fuel milleage was the same,maybe even better.Even if you did lose some mileage,and I doubt it,the power increase is well worth it,you won't be sorry you put it on that's for sure!

Mine went from 38 mpg to 28 mpg with the 32/36. If yours Weber is professionally tuned you might be able to get the same mileage -- if you avoid ever "flooring" the pedal.

mine had no impact on the highway. Lost a bit around town, but thats expected because you're making more power.