Why we use cotton cloth in summer?
It gives you more breathing room and will keep you cooler.
We don't. We use cotton all year long!
Cotton is a natural fibre and it is cool and breathable. Man made fibres like polyester are not breathable and cause heat and perspiration.
You can use automotive oil but I would not recomend it.For the fuel any decent 2-stroke oil from a small engine or auto shop will work fine.