First, a spark plug color chart is the same for cars, mowers, motorcycles, 2 stroke or 4. It makes no difference. When an engine is designed, the proper heat range plug is chosen, and rich is rich, lean is lean, and the color of the plug reads the same for all types of motors.
Second, I've never seen a small engine maker ever suggest anything but regular gas. Timing on these engines is fixed at a certain point to coincide with the rate of how fast the gas burns, in this case, 87 octane. On an engine where you can manually change the timing, you can play with the octane of gas you use by changing the timing, but you can't do this with these engines. What you can do is use a better brand of gas, but stick with the suggested octane.
And now my suggestion. Use Sea Foam in all your lawn equipment, if not every engine you own. The reason? Ethanol. In some situations, ethanol can clean an engine, actually dissolve carbon. But in the combustion process, ethanol actually promotes carbon build up. A product like Sea Foam can help carbon from forming in the first place, and in time can rid your combustion chamber of carbon all together. The hotter an engine runs, the more carbon build up can occur. Your car runs fairly hot. An air cooled engine(mower) hotter, and your trimmer(2 stroke) even hotter.
And for a proper mix, find a product that does the math for you. You can usually can find one at a motorcycle shop that caters to dirt bikes(that means NOT a Harley shop). A lot of dirt bikes are 2 stroke, and many use different mix ratios. They are easy to use. Knowing the size of the gas can, you pour enough oil to the line next to ratio you need(50:1, 32:1), and pour it in the can. NO MATH! The one I use is called a Ratio Rite Cup.
