Increasing Oil Weight in High-Mileage Engine

My ‘90 Bonneville came with 5w-30 out of the factory, and that is the recommended weight. However, I’ve had something knocking for years, and want to get it quieted down so I can get a few more years out of the car. A co-worker recommended I switch to 10w-40. Mileage is 227,914 miles. I read that engines using hydraulic tappets need a thinner oil. Also, the engine is pushrod, not overhead cam. Would I benefit from increasing the oil weight? I’m running synthetic 5w-30 right now, just put it in a few days ago.

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