Oil light mystery on 2004 Yamaha R6

Q. I have an ’04 Yamaha R6, and on cold mornings the oil light comes on for about 30 seconds after I have been riding for a couple of minutes. When the bike has done about three or four miles or when engine is warmed up a bit it stays out.

This only happens in the winter months. I change the oil and filter regular every 5-6000 miles and always use semi-synthetic oil. Sometimes different brands but always a top quality one.
Scratchme, MCN forums

A. The oil light on the R6 measures the oil level, not the pressure from the pump, using float activation. As the light stays off once the bike has reached operating temperature we don’t think that there’s anything wrong with the system.

It’s just that the oil is more viscous when cold and will take slightly longer to return to the sump, allowing the oil light float to drop and activate the warning light. Once the oil is hot it returns faster and the float level stays stable.

A couple of factors that will also influence the above are the grade of oil and oil level. 10W 40 would be the best grade in the UK (do not use less than 10W or car-type/energy saving oils).

15W and 20Ws are not ideal base weight oils in winter. If you set the oil level to the upper level that will probably be enough to prevent the light coming on.