Higher octane fuel
 

Hi,

Just wondered since owning a 2.0ltr v6 and now a 2.5, I have being filling the tank more so with the higher octane fuel now and then, so generally there is mix of both in the tank, but is it worth the extra money? Is it better to fill the 2.5 all the time?, or are these companies hyping this stuff a bit much:shrug:, (cleaner burning, extra MPG etc)

Just wondering what your thoughts are on this, I have to say that she does seem to respond a tad better, but this could well be a placebo affect maybe:shrug:

Thanks.

You will find differing opinions here but I have been using Super-Unleaded, or the equivelents in all my cars since it became available about 10 years ago.... In all cases I found the car ran smoother, and was generally more econmical with slightly improved performance.
But it does take time to have an effect as the ECU has to learn the high octane fuel, which takes about generally a tank.

Of course you will find people will argue the toss about this, but this is my findings, and I've been using it for years.

Also I try to keep to one brand/garage where possible.

[/SIZE]Just curious but how does the ECU know what octane fuel you put in as it injects a quantity of fuel to a measured volume of air ???

Because different octane fuels burn at different rates/temperatures, so the ECU has to change the timing to achieve optimum performance.
It doesn't actually measure the octane, but the results of its use. This takes time.
I thought this quite obvious.

Do the petrol engines have knock sensors then?

I remember reading a test done by a magazine using a track in germany with all sorts of test and measuring equipement. The conclusion seemed to be it depended on what sort of car you had, the newer the car the more impact it had. The new range of small petrol engines with turbos fitted did the best. I don't think on old petrol engines like ours it would have much difference.

I used to have a SAAB 900 Turbo (GM) and it ran much better on the premium fuel, MPG worked out around the same (£s per mile).
As Mr Doodles says, the ECU advances/retards the ignition depending on the octane, but this can only be done in conjunction with a knock sensor.

The V8 doesnt have one ( a knock sensor) so there is no point on these engines, not sure about the others though

I am curious now, is there anything we can do as drivers to help the ECU learn quicker via our driving styles?

There is a knock sensor the KV6, however their is much debate on if it advances and well as retards timing. I do not know the definitive answer, it would seem pointless to not advance as 95 ron is our standard fuel and I would see little point in retarding only as we have good fuel in the UK.
What I would add is that as far I as I have been able to establish shell V power is the only fuel now to contain no added bio elements, there is a move in the eco warrior lobbists to get higher and higher amounts added to our fuel. V power is also the only fuel that is processed by shell in there own refinery other fuel comes from a common refinery with propitiatory additives mixed in at the refinery before delivery to the company. I use v power unless there is a silly offer on fuel at tesco/morrisons/sainsburys.