Then I'm sure that the bearing clearances are looser from the factory. I've seen newer motors calling for as light as 5w20.

I've had to pour some 15w50 oil when it was about 40* outside. It took me about five minutes to empty a quart bottle into the crankcase. It's just unnecesary. Honestly, the 0w40 that I had in the Camaro was probably too heavy for what I was doing also.

But in any case, do whatever makes you feel more comfortable. If you use oil that's too heavy the only downside will be loss of power from pumping. In extreme cases maybe a little more wear on startup because the oil won't pump to where it needs to be fast enough.