The only difference between fully and part is the breakdown time and suspension time of the additives. When oil starts to break down, due to age (water absorption) or heat/use the additives start to separate from the base oil. The base oil becomes contaminated with carbon deposits and this reduced the adhesion of the additives to the oil. If keeping to specified mileage/time oil change interval then all will be fine.
You do know that "fully synthetic" isn't "fully!!" The synthetic quantity of the oil differs between the oil giants, "fully" is just marketing ***** for the most part.
All the articles you'll read about the "advantages of fully synth" will funnily enough be on oil manufacturers websites!!! Or be written by an associate for the promotion of OIL!! Independent tests have only ever shown a difference between cheap and expensive oil manufactured to the same specification when left beyond the recommended change interval or when being used in a highly tuned engine. Other factors are temperature on cold/hot starts. If you live in the arctic or on the equator then the additives and "fully" help to maintain the oils specification for the time/mileage interval quoted by the engine manufacturer. Matey in the West Midlands will be fine with semi synth!
Super duper coloured oil with magnetic particles and friction reducing additives are manufactured for people who know very little but like flashing lights and pretty pictures, the marketing firms love that, it keeps them in business.
Oil tests performed in a lab are a far cry from you and me driving to and from work everyday, they try and simulate the conditions. Ask mechanics who deal with the stuff everyday. They will tell you "correct grade and at the recommended interval".
If you want to know what an oil is doing, check these guys out at ya next oil change. https://www.theoillab.co.uk/product-category/oil-testing/engine/
You send them ya dirty oil and they tell you exactly what's in it. This is a good service for finding out how much engine wear you are encountering.