As Kevin said above. Cheaper Weedeater grade oils leave lots of ash and carbon. Also plug range is important! I run an 8 series in my scoot and it is slightly carbon coated. I use Yamalube 2S brand oil. It is a synthetic base oil that burns clean. If I use a 7 series plug in my 2T however...it runs hot! Overheats...soft seizes and the plug comes out ashen gray or a bit white. I agree with avoid the Lucas stuff. Their 4T oils and oil products are great. But the 2T stuff separates if pre-mixed just like Castor based oils do also. Amsoil is my favorite oil..but hard to find where I live. Also NEVER use the TCW3 boat motor oils. They are designed for cool running liquid cooled engines. Sure most have a pic of a motorcycle or Scooter on the label...but unless those are liquid cooled..don't use it.
I used to use the Wal Mart little blue bottle oil...out of desperation while trying to find a good oil. It fouled my plugs even when used in my auto-lube system. Had to repack the silencer can on my tuned pipe twice in the first month because it became plugged with goo and unburned oil. The back pressure that created caused several HOT runs...which in turn soft seized one BBK 4 times. Not even a month old..I had to replace the BBK because compression dropped to 90psi and it would barely run...
