What's the optimal oil temp for 2019 Jetta?

A really general question as oils that are acceptable in the subject car can vary..... With conventional motor oil, 275 degrees Fahrenheit is considered a limit as hotter temperatures cause motor oil to break down and at around 350 degrees, they start to burn. The operating range for conventional oil is around 190 to 220 degrees, with performance engines going up to around 260. This range is more important today with modern engines having much tighter clearances than they used to have and use lighter oils that are more fragile. Common oil weight used to be 10W30; now it's 0W20. Synthetic oils can handle higher temperatures, but only slightly.

Oil temp too low and it doesn't lubricate well.