Why do people buy high octane petrol?

SlyReaper · 11 Nov 2011 at 15:49

Genuine curiosity here, not a rant. I notice a lot of you posting that you buy V Power or Super whatever petrol, but I can't see what you gain from it? By my understanding, your engine will either knock with a given fuel or it won't, and all modern petrol road cars are designed with 95 octane unleaded in mind because that's the "normal" fuel sold at petrol stations. So if it can use 95 without any problems, what do you gain from paying more for higher octane fuel? There's no efficiency savings, no power boost, just a lighter wallet.

Am I wrong?

Eriedor · 11 Nov 2011 at 15:53

Because my car is designed for 97

Vince · 11 Nov 2011 at 15:54

Because my car says 98 ron on the filler cap. So I feed her the good jungle juice!

Edit: I asked this same question long ago, basics are that modern performance engines can advance and retard timings based on the type of fuel.

Firestar_3x · 11 Nov 2011 at 15:55

This has been done to death, use the search feature.

burns · 11 Nov 2011 at 15:56

SlyReaper said:
Genuine curiosity here, not a rant. I notice a lot of you posting that you buy V Power or Super whatever petrol, but I can't see what you gain from it? By my understanding, your engine will either knock with a given fuel or it won't, and all modern petrol road cars are designed with 95 octane unleaded in mind because that's the "normal" fuel sold at petrol stations. So if it can use 95 without any problems, what do you gain from paying more for higher octane fuel? There's no efficiency savings, no power boost, just a lighter wallet.

Am I wrong?

Because if your engine does experience (and detect) knock it will prevent it by retarding the ignition. Which also reduces power.

So if for example it says in the manual to use 98 RON it will have been mapped to take advantage of this, then when you use 95 RON it will retard the timing to prevent knock, reducing power as a side effect.

Clarkey · 11 Nov 2011 at 15:57

for resistance to pre-ignition, that is all.

Do NA engines actually det or what?

Vince · 11 Nov 2011 at 15:58

burns said:
Because if your engine does experience (and detect) knock it will prevent it by retarding the ignition. Which also reduces power.

So if for example it says in the manual to use 98 RON it will have been mapped to take advantage of this, then when you use 95 RON it will retard the timing to prevent knock, reducing power as a side effect.

This is why good jungle juice = win... also you want to look like a Boss :cool:

while filling up and the only way to do that is with super.

SlyReaper · 11 Nov 2011 at 15:59

Okay, it seems I was wrong in assuming engines were always designed with 95 in mind. Thanks for the education.

I'll still be using the weak stuff to fill up the tank on my old Astra.

Vince · 11 Nov 2011 at 16:02

Clarkey said:
for resistance to pre-ignition, that is all.

Do NA engines actually det or what?

Mine is N/A..

Princey · 11 Nov 2011 at 16:03

I lost a substantial amount of American Gee-Gee's when running on Shell Fuel Save.

Vince · 11 Nov 2011 at 16:05

Princey said:
I lost a substantial amount of American Gee-Gee's when running on Shell Fuel Save.

Shell fuel save? Thats a 95 ron fuel isn't it? Am I right in thinking that in the US they use even worse fuel than over here?

burns · 11 Nov 2011 at 16:08

SlyReaper said:
Okay, it seems I was wrong in assuming engines were always designed with 95 in mind. Thanks for the education.

I'll still be using the weak stuff to fill up the tank on my old Astra.

Some old Astras have a special plug under the bonnet that you turn round to tell it you're running fancy fuel. Extra horsepower yo!

LSPIII · 11 Nov 2011 at 16:10

My car was remapped specifically on vPower

Even then, it says to use 98RON in the manual. Depends on the car really. Higher performance cars will recommend 98RON usually.

SlyReaper · 11 Nov 2011 at 16:11

burns said:
Some old Astras have a special plug under the bonnet that you turn round to tell it you're running fancy fuel. Extra horsepower yo!

Yeah, it would be awesome to add an extra half a horsepower to my three horsepower engine.

Begbie · 11 Nov 2011 at 16:12

Mine says to do so on the fuel cap, why am I to disagree over what £3-4 a tank? When it costs £60 to fill its hardly worthwhile not using it.

[TW]Fox · 11 Nov 2011 at 16:21

SlyReaper said:
Genuine curiosity here, not a rant. I notice a lot of you posting that you buy V Power or Super whatever petrol, but I can't see what you gain from it? By my understanding, your engine will either knock with a given fuel or it won't, and all modern petrol road cars are designed with 95 octane unleaded in mind because that's the "normal" fuel sold at petrol stations. So if it can use 95 without any problems, what do you gain from paying more for higher octane fuel?

I buy it because the manufacturer of my vehicle tells me it is the fuel they have designed the car to run on, and the fuel I must use to acheive the quoted performance and economy figures.

Pretty simple, no?

There's no efficiency savings, no power boost, just a lighter wallet.

Am I wrong?

Of course you are wrong. Why are you stating flawed opinion as if it were fact?

kaiowas · 11 Nov 2011 at 16:22

Many Jap spec engines are mapped for 97. As we have a Jap spec engine, with forced induction, being run on track why would I risk on using a lower grade fuel?

Lashout_UK · 11 Nov 2011 at 16:22

Because my engine is designed, assembled and tuned for it. To not use it could cause damage, at worst catastrophic failure.

Maccy · 11 Nov 2011 at 16:22

I compared filling up the Clio with normal and super on the drive up to Scotland in August. With super I could get 44mpg with the cruise on at 70, with standard I couldn't get past 38. Not a massively big difference but enough to convince me!

ci_newman · 11 Nov 2011 at 16:25

My Integra is specifically mapped for the 100RON fuel available in Japan. The best performance is available when running it on the closest fuel I can get to that, 99RON / Super.