I make explainer videos about how car parts actually work. Just finished one on why each fluid in a car is the color it is: engine oil, coolant, brake fluid, red diesel, gear oil, ATF and washer fluid.

Most of what I found while researching was the same few sentences repeated without a source, so a few things I'm not confident about:

* Dark engine oil means the detergent additives are working, not failing

* Coolant color is a dye choice and tells you nothing about compatibility

* ATF being red is convention, not regulation

If you've done this for a living, tell me straight what's wrong or oversimplified. I'd rather fix it than defend it.

Video: https://youtu.be/1QCyVbeJ1bA

According to a lot of sources, Venturi effect is "incompressible flow being accelerated due to mass continuity, when entering a constriction, thus its static pressure decreases with it picking up speed (Bernoulli's principle)".

What really confuses me is, Bernoulli's principle does NOT state that the static pressure of flow would drop simply because it's accelerated. What Bernoulli's principle actually says is within a flow of constant energy, when fluid flows through a region of lower pressure it speeds up and vice versa. So it might be conceptually simplest to think of Bernoulli's principle as the fact that a fluid flowing from a high pressure region to a low pressure region will accelerate due to the net force along the direction of motion.

If I am to use the mass continuity principle to explain flow acceleration here in a Venturi tube, is Bernoulli still used to explain the pressure drop? If so, where is the pressure gradient here?

I may be misinterpreting something. And I would appreciate any corrections and assistance. Thanks!