MPG: premium vs regular fuel

[I-S]

So.... Sad B'stard that I am, I record all my fuel data (how much, how many miles, fuel type, monies). It allows me to generate pretty little graphs that make me feel better about the fact that my car can't pull the skin off a rice pudding.

Anyway, I was at a bit of a loose end, so I decided to look in the numbers and see if premium grade fuels make any difference to fuel economy. I am not making any comment on other requirements for high-octane fuel (eg knock) - just economy.

Extracting the data, of the driving I have done of my GDI, 7781 miles were on 95RON fuel and 3386 on high-octane, either Vpower or BP Ultimate. I have used 234.35 gallons of 95RON and 102.63 gallons of high-octane fuel. Saving you all reaching for a calculator, that's 33.19mpg average on 95RON, and 32.99mpg on higher octane fuel.

Pretty insignificant, and well within the likely statistical variation of this data.

In terms of subjective difference, higher RON fuel is noticeably a little better in the GDI, letting it stay in lean burn mode longer (you can feel it going in and out) with a little more torque available in lean-burn. However, the cost difference means that it is not worthwhile imo.

Make of this what you will.

[g6acb]

that's 33.19mpg average on 95RON, and 32.99mpg on higher octane fuel.




I find it slightly the other way round - tesco 99 or v power giving about 5% more mpg - but the fuel costs about 7% more than standard 95 so whats the point????

[bradc]

Definitely well within variation on the mpg figures, I guess it depends if the 98+ gives you that much more power to make the cost worthwhile. I found in my 1.8 GDI it made enough of a difference make me always get 98

[I-S]

I suspect in a japanese spec GDI it would. In the UK spec, I think the difference is smaller (less lean AFR in lean burn, lower power, etc).

[bradc]

yeah, jdm's are designed for 100 of course :)

[Rambaud]

I don't have the same figures as Isaac, as I changed to superunleaded within a few thousand miles of my purchasing the GDI. I have done about 21,000 miles in total.

I have only used ordinary unleaded when superunleaded ha been unavailable.

I would guestimate my overall m.p.g. at ~ 32.00 (assuming little motorway mileage).

[The Vee]

Never really bothered too much with economy, but not noticed much difference (Yes the Scud has been treated to 95 on some occasions if just long motorway runs) Not very often now though that V power is around. I do find however, that the performance (for obvious reasons) is markedly better on the 98. Much crisper feel to the car.

[psbarham]

our jdm 1.8 yawn mobile gets super all the time and thats returning 30+ mpg on little 7 mile school runs, it definatly runs better on V power compaired to sainsburys super, tescos 99 or bp ultimate, but for the extra cost and for what it gets used for i can't justify the extra 10p per litre for v power vs sainsburys, oh and its a 40 mile round trip to get to a shell garage/Grrr