Spark plugs

[Tractor Rod]

I have a Farmall B with three spark plugs that are champion D15Y and the other is D18Y. Can someone please tell me the difference and which ones should be in my Tractor?

Thanks

[indy61]

For Champion brand plugs, the higher the number the hotter the plug. I doubt you will notice a difference but it's been said you want a hotter plug for a tractor that does not work hard.

[Tractor Rod]

Thanks so much!

[Jim Becker]

For light use, you probably would do better with the equivalent of a D-21.