So I just changed my oil from 5w30, (what the previous owner recommended) to Royal Purple’s 5w20 after some research. The weird thing that happened is now my S2 isn’t turning over as long as it used too. It’s not a real problem and I’m not worried about it, I was just curious if the oil weight or SAE vs. Synthetic had something to do it?

 

Assuming the purps is full synthetic, all you have done is lessened its protection at operating temperature.

If you are going that far it might be more beneficial to run a 0w-40, in my opinion

I use 10w-40 conventional or semi synthetic blend

 

Thinner oil reduces friction loss by oil pump.
Though both oil are 5w, 5w30 is thicker than 5w20 in cold, you can look up oil data sheet for viscosity at 40C.

 

How have I lessened protection at operating temp? Both oils have a 5 weight and RP supposedly burns cleaner than SAE leaving behind less carbon on the Apex seals. Not to mention full synthetics cause less friction. If anything I figured I was protecting my engine more due to less carbon and