I could be wrong, but I think the herbicide in weed and feed works by being absorbed into the leaves of broadleaf weeds. If that's correct, it wouldn't work as a pre-emergent. If you got it for free, you may as well use it, but in general, I think it's better to use fertilizers separately from weed killers and to spot spray the weeds rather than broadcast over the entire lawn.

A weed n feed will only kill broadleaf weeds in the present that it comes in contact with, not weeds in the future.

I agree it only kills what is their. Save it for the summer or fall.

You can use it if it's mixed with a true pre-m, like Dimension, etc, else you're just spinning your wheels...and by the way, it has to be put out no later than March 15th. Most everything else is POST-emergent, unless it includes synthetic chemical ingredients benefin, isoxaben, pendimethalin, atrazine, dithiopyr, trifluralin among others.

By the way, I usually put my pre-m out in mid-Feb because of the milder soil temps the last few years (any seeds in soil over 50F at 1 inch deep will germinate). That way I don't get a nasty surprise around May.

and it can't be used where shrubs and trees are.