I have a question about engine oil. I'm suppose to use 20w 40 oil for my TT-R250, but my one of my friends who has the same bike (03 bike) uses 20w 50 oil. I buy my 20w 40 oil from the dealership, but it's like 5$ per quart. I can just get 20w 50 from walmart for a dollar and something cents, but if I were to use 20w 50 oil when it recommends 20w 40 oil, would it ruin my dirt bike? Like I said, my friends uses 20w 50 oil when he's suppose to use 20w 40 and the bike runs perfect. He doesn't race or anything, just trail rides. I also just trail ride too. So I was just wondering what you guys think. I'm leaning to buying just 20w 50 oil for my bike because it's a lot cheaper, but it's better to ask before making a bike mistake.
