yeah F150 uses 18awg but 40 watts through it shouldnt be a problem, hell 40 watts should run through 22 awg without a problem. If he is planning on only running 40 watts per channel on 18 awg he will not see any problems. Yes I would upgrade the wire but I also would bother upgrading speakers to only run 40 watts, my comps are 100 watts ea and I run them on 12awg. but technically if you look at alot of comps that are sold that run 80-120 watts rms what do they come with? 18awg speaker cables, so he wont smoke his wires using factory for 40 watts.Not 100% sure, but isn't ford typically 18gauge? To make things easier? Come on, talk about half assing.