slant 6 oil weight

I run 10w30 in my leaning tower of power (slant six). The W in the oil viscosity code means winter, not weight. Also, the higher the number, the thinner the oil is. So, 10w30 oil will be thicker at start up temps than 5w30, which is what you want for optimum lubrication. The second number, 30, indicates that the oil is thinner at operating temps. Normally in these older engines you run 10w30 or 10w40, however, I would run 10w30 for most sixes and small blocks.