[jagh]

Hi all. Recently picked up a 2003 MCS in electric blue. Quite a nice little car.

Just wondering what fuel you guys use. Last few weeks I have just stuck to normal unleaded but was considering using optimax or similar. Has anyone noticed any difference? Perhaps with fuel economy?

Cheers,

Jag.

[David_MCS]

When using a Higher Octane Fuel i've always got increased performance and fuel enonomy. I'd definitely advice, as will others to use Optimax/Ultimate/Tesco 99 etc.

I'm a Tesco 99 fan, my MCS loves it

-David

[G-Man]

I used to use optimax, I now use v-power (if thats what they call it now). If I can't get a shell garage and haven't got enough fuel to find one then I'll use superunleaded or similar.

G-Man

[jagh]

Cheers guys. After how many fillups do you reckon I'll notice the difference?

[minicabrio]

I've always run my Cooper on Tesco 99 or BP Ultimate or OptiMax. On occasions when funds didn't allow or i was caught short and filled up with standard unleaded or god forbid supermarket unleaded she didn't feel any where near as smooth or powerful.

I'm happy to pay the extra, especially now Tesco 99 is down to 90.9p/l in Aldershot!

[No16]

The only advantage of high octane fuel is that it can withstand higher compression before it self ignites, it also burns slower. How does this give improved perfomance better mpg?

The air/fuel mix doesn't burn instantaneously when the spark plug sparks, therefore if your spark plug ignited the mixture when the piston was at full compression (TDC) then the fuel mixture wouldn't have fully igniteted until the piston was well on its way down. thus reducing power and effiecency. So the spark ignites the mixture before the piston has reached TDC otherwise known as advance timing.

With a supercharged (or turbo) engine such as the S the air inlet tempuratures are very high despite the intercooler (hence intercoolers) therefore i would always recomend using a higher octane fuel to prevent early detonation of the mixture, HOWEVER...

It all depends on how the car has been mapped and if it is equipped with a knock sensor. If the ecu has been mapped to to allow for slower burning higher octane fuels it will advance the ignition timing to get maximum efficiency out of the mixture. If not then there is no point spending the extra amount of cash on higher octane fuels.

My JCW S comes with a certificate that does recomend using high octance fuel so maybe it is cappable of advancing the ignition so far as to gain an advantage, or more likely this is due to higher compression due to supercharcher changes. Do mind though that this advancement normally takes a good few tankfulls of petrol (from past experiance with other cars) and if you then use a lower octane fuel and the knock sensor detects knocking or pinking ( where the mixture ignites too far infront of TDC, as the piston is rising) it will dramitcally retard the timing to get rid of it, thus another few tankfulls befor its back to normal.

So i don't know whether higher octane is better or not for this engine. Certainly wont do it any harm, just a question as to whether its worth the extra cost.....me its a fun car and 19mpg with v-power is acceptable.....going on a long family journey i'll take my diesel octavia

[Root Ginger]

Quote: Originally Posted by No16 (original)

The only advantage of high octane fuel is that it can withstand higher compression before it self ignites, it also burns slower. How does this give improved perfomance better mpg?

The air/fuel mix doesn't burn instantaneously when the spark plug sparks, therefore if your spark plug ignited the mixture when the piston was at full compression (TDC) then the fuel mixture wouldn't have fully igniteted until the piston was well on its way down. thus reducing power and effiecency. So the spark ignites the mixture before the piston has reached TDC otherwise known as advance timing.

With a supercharged (or turbo) engine such as the S the air inlet tempuratures are very high despite the intercooler (hence intercoolers) therefore i would always recomend using a higher octane fuel to prevent early detonation of the mixture, HOWEVER...

It all depends on how the car has been mapped and if it is equipped with a knock sensor. If the ecu has been mapped to to allow for slower burning higher octane fuels it will advance the ignition timing to get maximum efficiency out of the mixture. If not then there is no point spending the extra amount of cash on higher octane fuels.

My JCW S comes with a certificate that does recomend using high octance fuel so maybe it is cappable of advancing the ignition so far as to gain an advantage, or more likely this is due to higher compression due to supercharcher changes. Do mind though that this advancement normally takes a good few tankfulls of petrol (from past experiance with other cars) and if you then use a lower octane fuel and the knock sensor detects knocking or pinking ( where the mixture ignites too far infront of TDC, as the piston is rising) it will dramitcally retard the timing to get rid of it, thus another few tankfulls befor its back to normal.

So i don't know whether higher octane is better or not for this engine. Certainly wont do it any harm, just a question as to whether its worth the extra cost.....me its a fun car and 19mpg with v-power is acceptable.....going on a long family journey i'll take my diesel octavia

A couple of points. All MINI's (except One D ) are designed to run up to 98RON so below this will retard the ignition, lose performance and MPG.

It is a myth (on the MINI at least) that the car takes a while to readvance the ignition. Advancing and retarding igniton is done instantaneously.

Incidently I've found a drop in MPG since V Power was released about 30 to 40 miles a tank less

Tesco 99 has gave me back that MPG. Another tank of V Power, lost 40 miles driving again. Currently back on Tesco again. Gonna alternate a few more tanks before I make a decision.