Hi Muhammad, I can't assist with the rattle/grind sound but I am sure others will help with that as many good minds on here. The fuel consumption really has a lot to do with your driving style, tyres also pay a big part and most of all maintenance of the beast under the bonnet and transmission. I personally wont use full unleaded at any time unless really stuck with no choice, I use E91 and if the price is right E95, lately most petrol stations are not budging on price wars so all are expensive so E91 it is, when I check the economy read out my normal usage for short (COVID restricted) trips I am getting around 9.7L/100 this is pretty much the normal for me, as always there are days I just want to enjoy the power and the who cares about fuel consumption part of me kicks in and like Ashley said enjoy that power feeling. We have debates before about using the E98 verses E95 E91 so there will be some threads I am sure in the Aurion section to read, but if I recall most thought it really a waste of money for what you gain, I am sure when we can do some long drives a few more comments will be coming regarding fuel economy
Keep Safe
KAA