Bosch takes 50 cents to $4 off select Bosch Platinum IR Fusion, Platinum+4, Platinum+2, Platinum Plus, and Super Plus Spark Plugs via these mail-in rebates. (Click on the corresponding item name's link to get the proper rebate.) That's the best discount we've seen on these spark plugs. (We saw up to $2 off last year.) Rebates expire December 31. (However, the Super Plus rebate ends June 30.)

A best bet: Amazon offers its Prime members the Bosch 4501 Platinum IR Fusion Spark Plug (pictured), model no. FGR8DQI, for $5.98. Redeem the $4 mail-in rebate to knock it to $1.98. With free shipping, that's $2 under a similar mention from a year ago and the lowest total price we could find. (Non-members can spend $25 or more for free shipping; otherwise it adds $5.05.)

Amazon Prime membership is $79 per year; however, Prime is free for college students for one year, and free for parents and caregivers for three months.