is the use of engine oil additives (eg stp ) etc in the petrol engine of any benefit ? does anyone use these additives in their skoda ? if so does the engine run any quieter or smoother or any other advantages ? . any advice welcomed thank you .

All additives are snake oil, if they were needed the oil manufacturer would add them to the engine oil when it is made. They have been proven to cause engine damage to cars, and will void any warranty.

I wouldn't use oil additives even if i got them for nowt, years ago my mate used to swear by STP oil treatment, when he stopped using it the engine burnt oil for fun,he started using it again but it made no difference, the damage was done.