Which fuel should I use?

[phn]

I have a petrol 1999 MY Audi A6 2.4 V6.

Just wondering if it is worth the price premium to fill up with Optimax / BP ultimate / Tesco 99, with this car.

The engine is not exactly highly stressed (167BHP) is designed to run on 95, and will run on a minimum RON of 91 in emergencies, so would I really notice any performance or economy gains with a higher octane fuel i.e would the ECU adjust to the new fuel? Also would the economy gain outweigh the additional cost of the fuel?

For the record the A6 does about 29 MPG combined.

Philip.

[Mikey G]

Try a few tanks and see what happens, some engines respond differently to better fuels.

I used to get an extra 2-3 mpg out of my Seat when i used Optimax back then
It did feel a little more responsive aswell but it was designed to run 98 anyway.

[cara jynwyth]

Does it have knock sensing ignition?

If so, it will make a difference. If not, it will probably be a weeny bit down (fraction of a hp)

[rubbishbuyer]

I always find it difficult to tell when switching between fuels such as these, atmospheric conditions can affect the engines performance equally significantly. I know it sounds a bit too "scientific" but you might get a better idea if you consider this when making a judgement on which you prefer.