Originally Posted by Thefigus
I changed my plugs at 50k miles and they gap was way off in every cylinder. Ford is crazy recommending 100k intervals
Agreed, but that recommendation is for "normal" usage - which only applies on paper, because pretty well everyone encounters "harsh" or "extreme" driving conditions every day.
And with the computer controls on modern vehicles, you wouldn't necessarily notice a drivability problem until it's way too late. Better to maintain a regular, moderate maintainence schedule.
I noticed this with my last plug and wire change - there wasn't a huge, noticeable drop in drivability - more like a gradual erosion of performance - most noticeable AFTER you've done the maintainence (replaced plugs and wires) - and in checking the plugs, there was noticeable wear on the plugs (after around 100,000 km/60,000 miles).
Better sooner and more often than too late and not enough.