Will Super Unleaded Improve My Mpg??

[kgsric]

just been speaking 2 a mate of mine & he says he only runs his car on super unleaed (optimax etc etc ) & says he gets more power & mpg out of it than standard unleaded, Will my 1.8 sri getmore mpg/mph out of super unleaded, is it worth the extra coupla pence???

[yorkshireborn]

in a nut shell no but if u drove like a nun then yes u would

[Big Davie]

Ive always used super unleaded, until i found V Power from Shell, will deffo give a wee bit more umph....

Ive also found that im getting some mph more.....

[Ross DTi 2.2]

Simple physics dictates that if the fuel is more combustable (higher octane), it will take less high octane fuel to produce the same explosion as a given volume of lower octane fuel. Therefore you will definitely get better fuel economy from a higher octane fuel.

Your ECU through timing retardation may not allow the engine to produce more bhp from higher octane fuel. So while you may not get a performance increase, you will see more miles from each tank.

[parapaul]

Simple physics dictates that if the fuel is more combustable (higher octane), it will take less high octane fuel to produce the same explosion as a given volume of lower octane fuel. Therefore you will definitely get better fuel economy from a higher octane fuel.

Your ECU through timing retardation may not allow the engine to produce more bhp from higher octane fuel. So while you may not get a performance increase, you will see more miles from each tank.

I've been filling up with BP Ultimate Diesel since I had my Vec, so I have no comparison, but when I get my ECU remapped, will it make any difference that I'm running on a higher octane fuel? Will they be able to alter the timing while they're in there?

[Ross DTi 2.2]

Paul, there is no "timing" as such on a diesel engine as there is no ignition spark required to achieve combustion. On a diesel engine the explosion is created by compression. Injector timing may be able to be altered but I don't know if any of the current remaps incorporate this.

The BP Ultimate Diesel gives extra power by having a higher cetane (diesel equivalent of octane) rating than standard diesel. Given that there is no ignition timing to retard, the only thing stopping you from gaining power from this fuel is the amount of air available to the engine.

Diesel ECU remaps take no account of the type of fuel used, they generally just increase the fuel rail pressure thereby putting more fuel into the cylinders with each injector opening. Its not possible to account for cetane rating in a diesel remap as the ECU doesn't have an ignition map and this is what is adjusted along with turbo boost and wastegate actuator pressure on high octane fuel petrol engine remaps.

[kgsric]

thanks, do u think the extra miles will outt weigh the extra pence per litre for hight octane petrol?

[Ross DTi 2.2]

I'm not sure about the difference it'll make on a Vectra 1.8. My SEAT Leon Cupra used to get 50 miles per tank less when running on standard unleaded so it was roughly equivalent to 7 litres of fuel better off on super unleaded.

7 x 90p = £6.30
Extra cost of super unleaded 3p per litre. 3p x 55(size of fuel tank) = £1.65

£6.30
- £1.65
= £4.65

So I was saving £4.65 per tank by using Super Unleaded. Standard unleaded may be cheaper but it can often be a false economy.

[parapaul]

Ross,

Thanks - one of the best things about this forum is the ppl who can really explain things, rather than just give a yes/no answer.

[Timkel]

i used to run my mondeo v6 on optimax,and i averiged(spell check) an extra 30 miles out of a tank full.