No, absolutely not, unless it is a 4-cycle engine. Most homeowner weed eaters are 2-cycle, meaning that you must mix oil with the gas. if this is your case, use the expensive 2-cycle oil. I assume the higher price is the incentive for asking the question. 10w-30 has additives which will cause incomplete combustion, soot, etc.
Yea
You don't use oil, you use grease
Yea
none
50:1. Be sure to use 2-stroke oil.
3.4 fluid ounces
40:1
10w30
10w30
5w30 or 10w30
If the recommended oil is SAE30 why would you use SAE 10W30? Some mowers recommend either of these weights but if your recommends 30W then using 10W30 will cause it to use oil.
It depends on the brand of trimmer you bought. Stihl, Echo, Husqvarna use 50:1, or 1 gallon of GAS to 2.6oz of 2-stroke oil Weed Eater, Poulan, and Poulan Pro use 40:1, or 1 gallon of GAS to 3.2oz of 2-stroke oil Ryobi's use 32:1, or 1 gallon of GAS to 4oz of 2-stroke oil