it is the additives they put in the oil
Motor oil is rated many ways. One is the API rating for gasoline motors. SJ is better than SH, SH is better than SG, SG is better than SF. etc. So as long as the letter comes later in the alphabet it is ok. However the most modern oils ( e.g. SM) are not suitable for old engines.
Commonly 30W of SG or higher rating
Suzuki Manual for a 2006 M50 (VL800) States: 3.6 Quarts with filter change 3.2 Quarts without filter change Use 10W40 SF/SG or SH/SJ motor oil
No, you cannot use ordinary car engine oil. Use a JASO MA or MA2 approved oil, or SAE SF or SG graded oil.
It depends on if it is a manual transaxle or an automatic transaxle. If it is a manual transaxle, you can use any SG-rated 5W30 motor oil. If it is an automatic transaxle, then you need DEXRON II Automatic Transmission Fluid.
You can use 15-40 W oil of JASO MA or MA2, also SAE SG-SF graded oil intended for motorcycles.
SAE 10w-40 API SF or SG oil. I would recommend you use synthetic.
A 10w40 oil with an American Petroleum Institute or API rating of SF or SG.
Generally, 30W of SG or higher rating.
This answer depends on what the temperature will be in the area you will use the car. All suggested oils are API SERVICE SG, SG/CC, SG/CD, SF/CC, SF/CD Energy conserving II or greater for gasoline engines. If the temp will always be above 0°F, use 10W 30 OIL. (This is the most common) If the temp will always be cold and never above above 60°F, use 5W 30 OIL. If the temp will always be hot, and never below 40°, you may use 30W OIL. Cadillac Man
Use any JASO-MA or MA2 or SAE SF-SG oil of W 15-40 for this bike.