5w40 in the Lexus synthetic gets my vote. Not only will it provide you with great wear protection, it will keep the engine cleaner longer. Plus possibly increase your mileage a litte.
And Yes, i think it will protect you just fine in 50c temps.
The 5w is for cold start protection, and the lower this number is, the better. For you, i don't see the need to go lower. But a 5w would be good in this engine due to it's high rev's at startup when cold. I'd imagine your's does this?
The 40w is for operating temperature protection, when the vehicle is hot. I don't think i'd say a 50w would protect better, but i'm just a novice at this stuff. But i'd be willing to bet a 40w synthetic would protect better than a 50w dino.
And Yes, i think it will protect you just fine in 50c temps.
The 5w is for cold start protection, and the lower this number is, the better. For you, i don't see the need to go lower. But a 5w would be good in this engine due to it's high rev's at startup when cold. I'd imagine your's does this?
The 40w is for operating temperature protection, when the vehicle is hot. I don't think i'd say a 50w would protect better, but i'm just a novice at this stuff. But i'd be willing to bet a 40w synthetic would protect better than a 50w dino.