summer oil
#1
#2
All depends on what the mfgr calls for. Without an owners manual the usual and customary is ...with an aircooled engine a heavier weight oil is needed as oil breaks down with heat unless you move to a full synthetic oil, then synthetic oil has no heat breakdown. With a liquid cooled engine a slightly ower viscosity oil can be used as the engine should run cooler in the summer heat. Aslo where are you riding?....if out west in 100 degree heat then a heavier oil is needed but if avg daily temp is only 80 degrees then a lighter weight oil can be used. On my personal machine (liquid cooled) I simply use a full synthetic oil, 10w-40 all year long or a 10w-30 is also called for. If your using a straight dino oil then refer to the mfgr recommendations. I would guess that a 15-40 oil would be quite suitable unless you have an air cooled engine then a 20w-50 might be in order.
#3
Here's my suggestion:Shell Rotella T6. I use it in all 3 of my Arctic Cats, 400 and 500 Suzuki motors and 700 diesel. Sending a sample to Blackstone Labs, shows me that wear metals are way down compared to 10w40 Motorcycle or Mobil One synthetic. Here's a report on my AC 500= 1st oil was Maxxima 10w40 motorcycle oil, 2nd Mobil One European formula, last was T6.