I a newbie to sight glass oil reads so wrote Paul for clarity.
"If you can see oil in the sight glass, you are fine. When you see white in the sight glass add about half a quart. It is a fool proof system. Even when you can't see any oil in the sight glass (i.e. it is all the way below), you still have a lot of oil in the tank. Don't sweat it.
There is no "weight" to two stroke oil. There are several different versions, depending on how good the quailty of the oil is. All of them are fine. I only use sythetic though, it just provides much better lubrication. I think I usually use Motul 510, which is their mid-range oil. I think it costs around $15-20 per quart. -Paul"
With regards to oil Gianluca said, "I always use supreme gas for my scooters and the best oil for two stroke engines. The glass bubble shows oil when sufficient quantity is stored. Even after the bubble shows air, you still have a safe amount of oil to make it to your next re-fill.
Motul 710 is the only oil we use.
Spark plug replacement was performed in late June 2011 with 8,064 miles on the odometer.
Ciao, G."
I picked up Motul 710 and three spark plugs per Vespa P Series Maintenance & Repair. I believe I bought three B8ES. I am interested in checking out the Iridium spark plugs as I have heard they provide a little more power and a better idle.