Insensitive *****

In the UK 10w40 is generally recommended for ambient temps of 5-30C. For whatever state you are in just google which viscosity is best for you.
With regards to changing oil, I'd say every 2-3000 miles for dino/semi synthetic or every 2-5000 for full synthetic oil or if you cover neither of those mile limits a year, just change oil annually right BEFORE putting bike into storage.

Change filter with each oil change too, after all you wouldn't take a shower then put the same used underwear on afterwards.

Yep, you need oil in the bike or big problems.

Here's my two cents.

I'm on my third C50 engine. First one had 80,000+ miles and was running fine when a lady pulled out of a parking lot & clipped the bike. Second one I got to 115,000 miles before the timing chain stretched far enough to skip a tooth. Third one (installed in frame of bike two) I have about 50,000 miles on so far.

I get my oil at Dollar General. Just the cheap store brand 10-40 that doesn't say 'energy conserving' on the back of the bottle. I was getting it at Family Dollar and then one day I noticed their store brand had gone to an 'energy conserving' formulation. I use my bike as my main transportation & commute 100 miles a day, in all kinds of weather, all year long. I change the oil every 3500 miles. I used to change the filter every time; but switched to every other time several years ago.

I've heard it said that oil will oxidize over the winter and you'll have to change it again come spring..... hence, that's when I change mine.

Isn't it amazing how motorcycles existed-and ran perfectly fine- for well over 100 years before marketing executives invented "motorcycle oil"?

After the Arab oil embargo in the 1970s. fuel efficiency became a top priority to auto manufacturers. Engine oil producers began adding friction modifiers including molybdenum, teflon, graphite and others to help the engine run more efficiently. The downside of this formulation is those solids got trapped in the clutch material of wet bath clutches. This caused them to slip and they have to be replaced once they become contaminated. Motorcycle specific oil is much more than marketing to get you to pay more for oil.

Wow. Wouldnt surprise me if you have put more miles on the C50 than any other member. Just goes to show how long they can last with regular maintenance and care.