What grade full Synthetic Oil? Amsoil 10W40 vs 20W50

[wsk3]

My dealer's service dept. put in Castrol Power 1 Racing 10w-50 at my first oil change.

 

[steve59]

I used amsoil 20w50 last summer and the starter cranked fine cold I use it whenever I can get it but like a previous poster said I use 10w40 when its colder. As far as spectre platinum My dealer put it in my Storm and returning from atlantic city to chicago the top end noise was terrifying I was cruising about 3200 rpm and the metallic sound made me consider stopping still 180 miles away and having it trailered. I rode it home anyhow put decent oil in it and couldn't repeat the noise. I asked around about the "camchain type sound' and the most sensible response I got was the oil broke down. but at under 2000 miles!

 

[Scuba Craig]

Just looking back at my receipts, I have used Castrol Power 1 Racing 5W-40 for the last 2 oil changes. Both times it was the oil recommended by my local Triumph dealer.

 

[Idaho Red Rocket 3]

The cold air/engine temp rating is the first number. Hot engine temp rating is the second number. We like to have thinner oil to start a cold engine particularly when the air temp is cold too. Some may be thinking old school dino oil characteristics. Modern synthetic oils behave differently. As I have read and it has been explained to me, synthetic oil will act "thin" cold and act "thick" hot. Supposedly when cold the synthetic oils will behave as thin oil when cold and thick oil when hot. So you need 10 to start cold and 50 when warmed up to full temp. Go with 10W/50 or 15W/50 if you can find it in a quality synthetic oil. I choose to stay with the Castrol 4T 10W/50.