I've got a Q-jet. If I buy a rejetting set and install secondary metering rods that say it will make it leaner, is it guaranteed to make it run leaner (though not guaranteed to increase performance or mileage), or does it just depend on how the carb reacts? That's kind of a confusing question to word so sorry if it's hard to understand.

How often should I change my fuel filters? I've got one in tank, one inline in the engine compartment, and one in the carb. What about air filters? Can any of these affect gas mileage?

Thanks..

Leaning the sec rods/jets should lean the secondaries. That won't help gas mileage unles you drive with them open all the time smile.gif .

I'd change the fuel filters at least once a year. They probably won't have an impact on mileage but can affect driveablity.

The air filter can have a large effect on mileage. With a paper filter I've always been told that when light will no longer pass through them they need replacing. Personally, I've never let them get that bad. In a dusty environment change it often. I highly recommend a K&N or one of the copies. They flow really well and last nearly foever. According to K&N they will flow and filter fine up to the point they have 1/8" of dirt on them. K&N recommends cleaning their filters every 70,000 miles.