If you have a multimeter you can check for resistance in your plugs by placing the leads on the center electrode and the terminal on top. If it is non-resister it will read very close to 0 ohms. I checked several small engine resister plugs and they are showing about 22k to 24k ohms. One was a brand new Champion RJL19LM still in the box. I checked one non-resister I had for my old race car and it showed less than 1 ohm. If I had sanded the coating off the terminal end it would probably have been 0. If the E3's show high resistance like this I wouldn't hesitate to use it.