Question: Can I use 15w40 synthetic oil in my 2015 vw jetta tdi and how long can go between oil changes?

Answer: 
Replace the battery and those issues will stop.

Reason? The bad battery is so discharged after starting the engine the alternator takes a few seconds to bring the system voltage high enough for some electronics to work properly.
For my 2000 toyota sienna (which has belt+fluid driven power steering) doing a complete fluid flush helped (turn the wheel back and forth 10x afterward to flush out air bubbles), FWIW...also probably worth making sure fluid isn't low first...

After that it's replace hoses, then replace pump, I guess.

ref: <https://answers.yahoo.com/question/index?qid=20090412100118AA3kc5m>