Hi,
I recently had my car serviced at 18,000kms, and it ran beautifully.
After filling the tank on the next occasion (using 98 octane fuel), it started to, well...no longer drive as effortlessly, as if I was using a fuel whose octane rating was too low. Nothing's actually 'faulty', but it's certainly not what it was before.
When the A/C compressor kicks in, the idle speed will sometimes drop too low down (around 600rpm) whereas normally it idles at around 800rpm. I remember noticing this issue back when the car was newer and my mechanic advised me to switch to a higher octane fuel (which I've been using ever since, and it has worked).
Could I have filled up with a dud batch of fuel? Could it be that the reservoir was connected to the wrong pump at the station or something? Perhaps the oxygen/knock sensors are not working the way they should be, so that the timing is not retarding as much as it should with leaner fuel. This engine uses dual knock-sensors from my understanding.
I will try adding octane booster to the current tank of fuel and see if this helps, but I suspect that the knock sensors are not doing their job, somehow. Any advice, opinions or feedback would be much appreciated.
FWIW, I've just switched from a mineral blend oil to full synthetic, if that helps.
Michael.