I went to extent of checking resistances in a variety of manufacturers new unused plugs all same application. The only consistent plugs were ngk's all about 5000 ohms. Others were wildly variable in several cases. I put some ngk's in one of my darts and immediately saw improved starting and engine runs a wee bit cooler as well, (slightly colder plug installed too). I won't use anything else after that. Small engines run better with ngk's too in my experience.