Lately my truck's seemed to be a bit slower, less mpg and in looking at my records I realized it's been about 2 years since I changed my sparkplugs myself, but in aug last year on a long trip my truck had a melt down and I needed to get it fixed out of state. The shop changed the rad and cooling system but also put in a new #3 coil and apparently a new sparkplug in that single cylinder. I only found out just today when I changed out all my plugs and put in NGK v-power plugs. The #3 plug was an NGK platinum plug, with the gap at about .05 instead of the factory .031 gap. All the condenses down to a few questions:
1) can mixing plugs like this do anything harmful?
2) are the platinum plugs any better than the standard ones?
3) how much performance is lost with a larger plug gap?