I use Valvoline VR1 20/50. They make other weights. I can't say it's better but is high temp and high zinc and formulated for flat tappet engines. I can't prove it but think my oil pressure is better under load with it. Meaning dealing with heat. I used Rotella but noticed it went dirty very fast, meaning it turned black and seemed very thin at temp. The VR1 has remained cleaner (visually).

 

Shell phased out T3 and only offers T4 now. That's why you get redirected.

 

Rotella gets dirty faster because the detergents in it are picking up more debris from your engine.

 

My Rotella is still clean when I change it at 5k on my 7.3.

When I had motorcycles i ran it on all my bikes from a 75 honda cb550 to a 2008 Ducati monster. I never had issues with it turning dark. Dark stained oils make the sight glass impossible to see in bikes.

That being said, when I've purchased neglected engines that were full of sludge it took several oil changes to get clean oil changes. A little sea foam in the crank case and a good 30 min run time before oil change helped speed this "cleanse" up a bit. Marine small block Chevy motors from the 80s and early 90s are among the worst for neglected oil change intervals and cheap store brand oils.

I have had customers complain that their oil is still dark after we do an oil change on their outdoor power equipment. These are always the ones that hadn't changed the oil in several seasons. It turns black again almost instantly. The kawasaki branded oils we sell are very much the opposite of cheap.