Using more petrol? Unknown reason :( Options

[Liam_c]

Hey everyone

Lately my car has been using more petrol than what it usually would, and i have no idea why.

When i bought the car, i was running it on 91 octane, and it was using about 8.5 L per 100km, and then about 2 months ago i upgraded to 95 octane and it was using 8.1L per 100km. No mater how i drove it on 95, it was doing high kms every tank i was loving it

But recently, its jumped back up to 8.5L per 100kms, and even though im driving it nicely, its still using alot of petrol. I started to notice it shortly after i had taken it on a car club run about a month ago ( driving around the hills, giving it a bit of stonk in the hills)

To some of you, this may not really be a problem, but its worrying me as i don't want it to get worse (and on my current run, it seems to be getting worse )

Where would be a good place to start looking for what could be causing this issue? I'm 90% sure it isn't a leak, as there is no noticeable marks on the ground after being parked up.

Air filter? Catalytic converter? Wrong fuel type? Fuel filter? O2 sensor?

Thanks

Engines a 3sfe.

[Liam_c]

Thanks for the input guys!

I reset my ecu last night and then filled up with bp's 95 (shhh, i work for an opposition ) so ill see how this run goes.

My cars getting a WOF at work next week, so i might ask how much it will cost to get spark plugs done, filter, etc.

I've recently done an oil change, so it may or may not be having an effect... Im using magnatec 10w-40. Was like 60 bucks for 4L D: