I just bought a 2013 smart passion which has 34,000 miles on it. I'm going to change the spark plugs but I will use an iridium aftermarket plug. I just wanted to know what model Denso plug works in my car. I guess it's a 451.
I just did plugs today on mine. Used Denso 5353 Iridium plugs. But, the plugs I pulled out of them were Denso IXUH22 H9. Got them on rockauto. Runs great so far. I believe Denso is the original plug that Smarts have. Not NGK. Nothing should be wrong with NGK plugs, but might as well use what Smart uses.