Yes, they can be mixed.
The type of oil for a 1997, BMW 540-I is a synthetic 5w40 blend.
If you're talking the engine operating RPMs, 1000... 540 is idle speed. It's stressful on the engine to operate a PTO at that speed, plus running that low forms a carbon ridge at the top of the cylinders.
540
540
36% of 540 = 36% * 540 = 0.36 * 540 = 194.4
28% of 540= 28% * 540= 0.28 * 540= 151.2
37% of 540= 37% * 540= 0.37 * 540= 199.8
85% of 540= 85% * 540= 0.85 * 540= 459
12% of 540= 12% * 540= 0.12 * 540= 64.8
18% of 540= 18% * 540= 0.18 * 540= 97.2
The 2014 BMW Alpina-B7's engine produces 540 hp @ 5200 rpm.
50% of 540= 50% x 540= 0.50 x 540= 270