Following a fuel change my engine cut out after 3 minutes driving however I was able to restart and drive home for 8 miles. The car did drive quietly for those 8 miles. It does start however and it continues to sound quiet.
Since it wasn't my normal supplier, it cut out after the fuel change and has been quiet since, I thought it must be contaminated fuel. However it did start up, manage to go 8 miles and currently still starts up so I'm wondering if there might be a different cause e.g. low octane fuel.
In any case, How can I diagnose whether fuel has been contaminated and to what extent?
From my understanding if you just drain a little bit of fuel from the fuel tank and put it in a glass, u will see the water sink to the bottom of the glass and this will mean you have water.
If you have water but also have ethanol in your fuel then the water wont go to the bottom but will be mixed with the fuel in which case you don't have to drain it, it will go with time. Theres also the issue with sediments which I'm not sure how to test.
Basically I want to know how to diagnose it before I pay someone to drain it all. I imagine the symptoms described don't prove the fuel is contaminated or even contaminated to the point it needs to be drained e.g I guess it could mean there's a lower octane rating fuel etc.