High Octane Petrol

[roystonvasey69]

Hi All,

I'm new here so apologies if this topic has been covered off before... but has anyone experienced problems (or indeed benefits) of high octane petrol? I'm running a 2001 Avensis 1.8vvti with 97k on the clock, and it normally runs like a dream.

Recently travelled from our home in East Yorkshire down to my parents on the Sussex coast. On the way back, and purely to try it, filled up with Tesco Ultimate 99RON petrol. Very smooth running, and seemed to get 2 to 3 mpg more than usual, but... within about 10 miles of filling up, the engine warning light came on. No option but to carry on (up against time) and since the engine was running fine, I crossed my fingers and went for it. Two weeks later, the engine light is STILL on but it continues to run fine. I have since refilled with normal fuel, by the way.

My local garage can't find a problem (even via the diagnostics), but obviously a fault is registering somewhere. Anyone had experience of this? Could it be a totally unrelated problem and the petrol thing is a pure coincidence?

Appreciate any help. Thanks! :)

[Red Yaris 54]

Please modify the font that you are using as it is difficult for some users to read :)

It is always advisable not to ignore warning lights particularly when they remain illuminated for so long

[BigMo82]

Surely if the light is on it must have registered a fault code of some kind?

Mo

[Radiodanno]

if the EML is on, then a trace code has definitely been generated on the ECU. The garage you've taken it too haven't read it properly.

Take it to somewhere else, or buy a code reader for £15 from eBay.

Failing that, take it BACK to the original garage and ask them to clear the code (the light will go off). If it comes back on you've definitely got an issue.

[roystonvasey69]

Thanks all. As a quick test I disconnected the Battery, left it for about 10 minutes, then reconnected. Started the car and the engine light went through the normal check cycle, then extinguished. After about 20 minutes driving, though, on it came again! Engine still running perfectly in every other respect.

There's obviously a fault signal being picked up from somewhere, so it's going back tomorrow for a fault code reading. Will let you know how I get on.

Thanks again! :)

[perdaniel]

Thanks all. As a quick test I disconnected the battery, left it for about 10 minutes, then reconnected. Started the car and the engine light went through the normal check cycle, then extinguished. After about 20 minutes driving, though, on it came again! Engine still running perfectly in every other respect.

This sounds like what used to happen when I had an oxygen sensor with faulty preheating. That should show up as an error code, but you can probably measure the resistance of the sensor. I'm not sure which wires and what the resistance should be, as I have a 2.0.