Sooo pity we don't have here british prices ... Here the market is small (regarding spare parts, etc) and prices for new one are quite high ...

Will you find here an obd scanner (new) for 60 CHF? This is purely impossible!

which is why you buy from ebay, they are all chinese / hong kong sellers anyway so your location doesn't matter, you may get hit with a customs bill but it won't be much.

A car mechanic who has had his own indie garage for 20 years.

(after re-thinking I decided to remove my post)

not wishing to question his ability, but , if he was a specialist in your particular make and model of car then I might, *might*, trust his diagnosis from just listening to the issue.

But

I guess he isn't, and the fact your engine warning light is flicking on and off should set alarm bells ringing in his head and he should read the code, even just so he (and you) are sure its nothing serious.

One of my cars was de-catted, every now and then the light would come on, and even though I knew what the issue was, I still blooming well checked the code to make sure!! (and turn the light off again) the problem with engine warning lights is they are binary, so once its on you could be having multiple failures living in blissfull ignorance thats its just 'bad fuel'

Yeah, I am not totally satisfied with his no-big-deal diagnosis. Will certainly visit another one soon, just wasnt in a hurry, since the lights havent come on since those first two times, and the shuddering seemed to be getting lesser too (could be just wishful thinking though).

We have had this problem from bad fuel or from not securing gas/petrol/benzine cap by giving it a double click. The error code came up and we cleared it. After that the gas thing cleared on its own, but I didn't go back to the same gas station for a while. However, I have never had a knocking sound because of bad gas. You may want to check the coil packs. I had misfiring on my Audi A4 sports one coil pack after the other broke, but they are easy to replace -my husband did it.