I have always used the “standard” Bosch “copper” spark plugs in our ‘89 wagon with good results. I change them when time comes and everytime I do change them, even tho the old brick may have been running smooth, new plugs seem to make it feel even smoother. Yesterday I changed the plugs but I installed Bosch SILVER plugs this time, W7DSR, at about $7 each. My mechanic recommended the silvers but did cite they are pricey. As expected the old engine felt even smoother with the new plugs, but unless its my imagination due to “mental suggestion” the motor felt smoother than ever, and the sound of it idling even sounds different -moreso like a well oiled sewing machine or a fine watch running-. Like I said, I know it could be mental suggestion, but I love it. Definitely more pickup, and btw, the old plugs looked in pretty good shape for the time they were there. So with that said, the test of time will tell. Just posting this FYI basically. We’ll see if $7 each really is worth it as time goes by. Im hoping for any increase of average mpg. I usually keep track of my mpg every fill up, so after about 10-20 fill-ups or so, if I do see an average increase in mpg, I might feel safe to think it’s the new type plugs.