Join Date: Dec 2014
Location: Brisbane, QLD, Australia
General recommendations are that synthetic should't be used until the engine is broken in. This is a particularly important time if you want the piston rings to seal properly.
In general, a good mineral based oil will work very well. If you are putting extra loads, rpm, and heat cycles through the oil, a synthetic may be worth considering. In most countries, oil companies are allowed to market their hydrocracked group 3 mineral oils as synthetic. Where a true synthetic will be a group 4 oil. If you really want a synthetic, then maybe you should be aware of this.
Essentially you can use any oil that meets the standards recommendations in the service manual. Oils are classified by viscosity. Higher numbers equal thicker oils. They are also rated by various standard bodies, e.g. API or JASO. API ratings are expressed as SA, through to current SN oils. This isn't so much a quality, but a technical application rating. For instance, oils of SG ratings can be of great quality, but not compatible with catalytic converters, they have too much zinc and phosphorous anti wear additives (ZDP or ZDDP). JASO ratings have become more important with motorcycles over recent years. Certain anti friction additives, and the light viscosities used in modern car oils, can cause clutch slipping and gear face damage in bikes these days. So any bike with a clutch that runs in the engine oil will need a JASO MA rated oil. This certifies that the oil is designed for use with wet clutches.
The real advantage with synthetic oils is their viscosity stability. multigrade mineral oils use viscosity index improvers. These long chain polymers knit together to help the oils viscosity properties change as the oil warms. It is these viscosity index improvers that break down through shearing and heat cycles. Because synthetic oils don't use viscosity index improvers, they retain their viscosity for a longer period of time.
That said, good mineral oils that are changed regularly will provide excellent engine protection.