Just seen a 5th Gear fuel comparison test whilst watching a repeat on Dave.

They tested a bog standard Clio, a Golf GTI Mk5 and an Impreza STi (MY06).

They reckoned that there was no effect on the clio as its not a performance car, the Golf gained an extra 12bhp using Optimax compared to std supermarket fuel and Impreza results were as follows:

Std Supermarket Fuel: 235bhp

Ultimate 97: 246bhp

V Power 98: 258bhp

I was very suprised to see this as its often difficult to tell especially when asking others what they think and getting very different opinions. I personally always thought the car goes better on V Power than when I've tried it on Tesco Value petrol and usually put V Power or other brands of 98/99 octane in it but wasnt sure whether it was just psychological and in fact a placebo effect...

What do you reckon?

 

Super unleaded will help turbo cars, especially ones remapped to allow for the likes of Tesco 99 and V Power but a normally aspirated car will see little increase.

I only ever used V Power in my S2000 for the extra cleaning agents .... it certainly didn't make it feel any quicker.

 

How could you tell if you've only ever used one make of fuel?

Try putting a tank of nasty cheap stuff in when your in the middle of nowhere, run it for a few days then report back when you have a basis for a comparison.

 

Also depends on the year of your car - Pre 2001 (I think?) were mapped for 98RON from the factory - put in normal unleaded and it definately isn't as happy.

Post 01 the law changed and new cars HAD to be mapped for 95RON standard unleaded.

 

You have read my sentence differently than I intended .... a better choice of words may have been more appropriate

I do have a basis for a comparison ...

I only used V Power for the cleaning agents ... I tried Tesco 99, normal unleaded .... you name it and I tried it .... and perhaps the most I could say is that the S2000 seemed smoother with super .... but is that just because I know I had put it in ?

 

If the ECU is mapped to take advantage of it is quite possibly, but its hard to accurately re-create the exact parameters on the dyno's ie one day could be colder.

Also the ECU could have still been learning pushing ignition timing then backing down ie it could have still be learning and a couple of days later it would yield less performance.

So in theory yes if the ECU is mapped and capable of taking advantage of it.

Jap cars usually like high RON fuel from Japan native 100RON.

Recently helped map a yaris t with my mate and we mapped it for 99RON, but god help him if he puts in 95 RON it in, we told him of the consequences but he just wanted the max performance.

 

95-99 is worth about 25BHP and 10% more mpg to me.
No point using 95 in a modern turbo with a good DME

 

I wouldn't dream of running 95 in mine, I'm pretty sure it feels stronger on 99RON - it definitely yields slightly better mpg.