Oil Viscosity by Brand

[DieselScout]

I went down a rabbit hole and started comparing spec sheets on different diesel oils. Below are the differences in viscosity at 100c and 40c for 5W-30 Synthetic oils.

Will any of these oils (based on viscosity) have a real-world, tangible difference in fuel economy, power, cold start flow, operating temperature protection, etc...? Or are the viscosity specs close-enough that they will all pretty much perform the same?

I've been running Rotella 5W-40 for the past couple of years and decided to give Amsoil 5W-30 a try this year. The engine feels much livelier with the 30 weight than it did with the 40 weight. (used in an '82 240 D24 NA)

Shell Rotella T6 5W-30 Mixed Fleet Synthetic:
12.1 @100
75 @40

Dello 400 XSP 5W-30 Synthetic:
12.1 @100
72.4 @40

Amsoil 5W-30 Synthetic:
12 @100
72.3 @40

Pennzoil 5W-30 Euro L Synthetic:
11.9 @100
71.7 @40

Mobile 1 ESP Synthetic:
12.1 @100
72.8 @40

Castrol Edge 5W-30 Synthetic:
12 @100
70 @40

[ngoma]

Originally Posted by DieselScout

The engine feels much livelier with the 30 weight than it did with the 40 weight.

What does this mean??? (engine feels much livelier)

I used to feel like my car performed better immediately after an oil change. Even with the same brand/viscosity as before. What did I base that on? "Seat of the pants" testing, fueled by creative (wishful?) thinking. Did it correlate with actual measurable results? Who knows? Are there ways for us to measure any conceivably tiny improvements?

[DieselScout]

By "Livelier" I mean that it felt less sluggish from a dead stop. Maybe it's a placebo or the weather.

Anyway, that's going down a different rabbit hole.

I'm just trying to understand the difference in 5W-30 oils available at the moment.

The viscosity numbers all look to be within a similar range to one another.
Are these numbers different enough to make any difference or will they all perform the same in regards to viscosity?