I don't know that heavy oil is used in competition like you think.
I run 10w-30 in my pull truck. We use oil heaters to get it hot before a run too.
Used to run a 0w-40 in our big modified gas pullers.
Most "good" circle track, nascar etc.. use very thin oil as well.
Thin oil makes less friction, less parasitic loss, more fluid lubricity, easier on cold starts etc.
A properly configured oiling system will work best with a lighter oil at temperature.
The people using heavy oil always run an oil heater or they would wipe out engines left and right.
Those top fuel guys don't leave the line at 10,500 rpm with 80* straight 70wt in their crankcase. It's 200+ degrees and flows pretty decent. They run such heavy weight oils because a top fuel motor runs "sacrificial" bearings. Which means they are designed to wipe away during a run in order to not damage the crank shaft. That's why they replace them every pass, there is no break in, they use super soft bearings and heavy, hot oil. That way they can make a pass and be relatively safe from bottom end damage at 8000hp and 10000+ RPMs. It's not the mode efficient oil strategy, but it's all they can do to keep them together. Not a recipe for longevity. And totally the opposite of what you want in a daily driver.
We no longer use 15-40 in anything at our shop. It's all semi-syn 10-30. Works great in heui's too..
