There is no need to use 10-40 over 5-30 oil, as a matter of fact the higher viscosity may make matters worse by not being able to get into the small passages thus increasing the wear.
Oil weight, or viscosity, refers to how thick or thin the oil is. Engines need oil that is thin enough for cold starts, and thick enough when the engine is hot. Since oil gets thinner when heated, and thicker when cooled, most of us use what are called multi-grade, or multi-viscosity oils. These oils meet SAE specifications for the low temperature requirements of a light oil and the high temperature requirements of a heavy oil.
Just my opinion.
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