I was looking at GoPowerSports' U-Tub channel just recently and watched their 'how to change the oil in your go kart' video. I was slightly astonished to hear them recommend my chosen
Pennzoil 30 weight oil as the one they use for all their demo vehicles. If it's good enough for them, it's good enough for me.
Furthermore, I was intrigued by the oil funnel they were using--the funnel top is graduated in standard and metric measurements so you just fill up the funnel to the specified amount and when ready you open the valve to let the oil flow into the engine via the long tube.
Without this handy funnel, you're constantly adding oil and checking the dipstick over and over and over again until you get it right. That's too tedious not to mention the hassle of getting oil into the angled oil spouts commonly seen on small engines. I had to get one--it's made by Hopkins Mfr Corp. and is called the #10704 Measu-Funnel.
https://www.youtube.com/watch?v=hAYOSDa753Q