Octane rating

[Freddy42]

I have always used BP higher rated petrol in the Focus Ecoboost despite its being about 10p dearer than 95, being reluctant to use supermarket versions. Petrolhead grandson suggested I might try the Tesco 99 octane, currently priced at 117p. This seemed to work wonders and the Focus shot off like a rocket. Any opinions about higher rated fuel?

 

[TCJBOLDIE]

Higher RON /MON fuels are good for motors with a high CR or a turbo running hi boost which increases cylinder pressures and raises the effective/final CR.
Just check my 8.7 CR and 20 psi CR
FYI I have forged rods and pistons and ARP studs to hold it all together.

http://goodvibesracing.com/Compression_Ratio.htm

 

[Rudders666]

I'd recommend either Shell Vpower or Tesco Momentum. Pretty much all I use in the ST.

 

[Lunchmoney]

Is your car capable of utilising the fuels ability to be compressed more? If not then there is no point in using a higher octane fuel.

 

[Freddy42]

Is your car capable of utilising the fuels ability to be compressed more?

Unlikely! It does seem to perform better nevertheless.

 

[Lunchmoney]

Unlikely! It does seem to perform better nevertheless.

That's very likely to be a placebo effect,

 

[SLEEPER]

momentum is 99 octane and it does have different additives but you need a serious engine set up and a dyno to be able to spot the difference

 

[drfuelinstein]

Octane ratings have been being discussed since the 1920's. In the USA they add RON and MON together and divide by 2 to get the rating posted on the pump. It appears the rest of the world uses RON rating today posted on the pump. I find it fascinating that Octane numbers are provided by testing in CFR engines designed back in the 1920's and 1930's. Back in those days those engine were not equipped with High performance High pressure fuel injection systems, computers and sensors or emission controls PCV, CCV and EGR. Has anyone on this forum done and reading about fuel aeration (Takes place in the fuel tank) or fuel cavitation that takes place in the fuel system and injectors themselves. We have known since the first part of the last century that there is a small amount of dissolved air in gasoline and it varies depending on conditions. A fish it swims in water, a fish it breathes air, Can we see the air? No because it is dissolved. This is a documented fact. My concern knowing this information is I am not so concerned what the octane rating is at the retail gas pump or even in my fuel tank. I want to know what the octane rating is when the gasoline is delivered at the injector. How much does aeration, cavitation and dissolved air reduce the octane number of the fuel?