So i just recently in the past year became an owner of 2008 4runner and I realized due to my reading in this forum of how easy it can be to do routine maintenance at home and save money. My last maint involved installing new denso iridium power plugs IKH20 and removing the previous denso iridium long life plugs SK20R11. Since then I feel that instead of any sort of positive in mpg it has actually dropped by 1-2mpg. Before I averaged 20 and now it's 17-18mpg. Anyone else have this problem? I know its getting colder here in TN and it can affect your mpg but I don't feel like it should change this much, it's only in the 40's. I also don't drive any different, mostly interstate and some in town driving. Should I go back to the long life plugs?