Why do people buy high octane petrol?

[TW]Fox · 11 Nov 2011 at 16:28

Maccy said:
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!

That IS a massively big difference, so much so that its impossible only the fuel was different. There will have been other factors that you were not aware of that caused the difference. You dont gain 6mpg in economy from switching fuel types on a normally aspirated car like a Clio 182.

Even the direction you drive can have an effect - I am never able to acheive peak fuel economy when driving down the M5/A38 when compared to driving up instead.

Maccy · 11 Nov 2011 at 16:31

Perhaps, but my driving style was no different throughout the journey. Having said that there was higher speed winds when travelling through the lakes so maybe that was working in my favour? Who knows. Either way, the recommendation for Clio 1*2s is 98RON.

Peerzy · 11 Nov 2011 at 16:46

Simples, Porsche (who happen to be a tad knowledgeable on the engines they build) tell me to.

I wouldn't run a 1.4 Polo on super stuff, but when it comes to high performance engines, I've paid £20k for a car I'm not gonna skimp out on the fuel for the sake of £2 a fill up.

SlyReaper · 11 Nov 2011 at 16:50

[TW]Fox;20541967 said:
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?

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

I was very clearly asking a question, not stating anything as fact. :confused:

JRS · 11 Nov 2011 at 16:51

VinceB1 said:
Am I right in thinking that in the US they use even worse fuel than over here?

Yes and no. In high-altitude regions, the highest octane fuel you'll find is 91 AKI (95 RON). Elsewhere, higher octane fuel is available.

PiKe · 11 Nov 2011 at 16:54

Mines quieter/smoother on higher octane.

Westyfield2 · 11 Nov 2011 at 16:56

My car is designed for 98 RON. The quoted performance and economy figures are for 98. So I... run it on Super.

My car has a knock sensor and will retard the ignition appropriately if I run it on 95, but unless I'm on fumes about to run out and the petrol station only sells 95 I'll always put Super in.

I did the Math last time I filled up. I paid £51.40 to brim it with V-Power. Had I used regular unleaded from the same station it would have cost £47.92. Wow. £3.48 saved. That'll what, buy me a couple of pints down the SU. Great. I'll splash out and use the Super.

Westyfield2 · 11 Nov 2011 at 17:04

Mathematical logic

SlyReaper said:
I was very clearly asking a question, not stating anything as fact.

SlyReaper said:
all modern petrol road cars are designed with 95 octane unleaded in mind

My car is designed for 98. It'll cope with 95 by altering the ignition, but it is designed for 98.

As Fox said, because there exists a modern petrol road car which is not designed for 95 you are wrong. http://en.wikipedia.org/wiki/Rule_of_inference

Mucky_Pup · 11 Nov 2011 at 17:05

Mines running a 100RON map, and it's only a couple quid more than 97, so go for 99 wherever I can.

Dogbreath · 11 Nov 2011 at 17:13

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

Do NA engines actually det or what?

Yes they certainly can suffer from detonation, and suffering from pre-igniton greatly increases the chances of it happening.

ScoobyDoo69 · 11 Nov 2011 at 17:28

Because higher octane does actually net more power and smoother running. The end.

Ivyforce · 11 Nov 2011 at 17:48

V Power is actually 99RON

In fact it will be slightly higher most of the time.

Peerzy · 11 Nov 2011 at 17:50

I don't use V Power, I simply realise I need petrol, pull up at the nearest petrol station and fill up with whatever petrol they offer at the most expensive price - is this much different to religiously using V Power (Which I'm under the impression is one single brand of expensive petrol and nothing more)?

Frozennova · 11 Nov 2011 at 17:51

Its old, and I put the best in, its a couple of quid difference in price.

Might explain the extra power over quoted figure it made at the OCUK RR Day, or the myth that VW engines gain power over time.

Westyfield2 · 11 Nov 2011 at 17:53

Peerzy said:
is this much different to religiously using V Power (Which I'm under the impression is one single brand of expensive petrol and nothing more)?

V-Power is Shells Super Unleaded product. It, and BP's Super Unleaded product called Ultimate, are meant to be better than the others Super Unleadeds... but the difference between different brands Super Unleaded products is not worth worrying about IMO.

Without going into the details some company's might be getting Super Unleaded by purifying their crude better, whereas others might be getting it by adding octane booster to their regular unleaded. The difference between this is not worth worrying about IMO.
Whereas the difference between regular and Super is, in a correctly mapped/CR car, worth worrying about.

The only thing I would say is that because of the reputation petrolheads buy their Super from Shell/BP, whereas Esso's average customer just buys regular... this can mean that Esso's Super is a bit older, been sitting in the tanks longer, compared with Shell/BP who have a higher turnover of their Super.

Overlag · 11 Nov 2011 at 18:13

because my car was mapped on 97

Ivyforce · 11 Nov 2011 at 18:19

frozennova said:
or the myth that VW engines gain power over time.

Which magazine did an article on super fuels back in'09.

They tested unl and super on a golf and focus.
Golf responded well to the super fuels.

2.1% power increase using tesco super over Tesco95
5.3% power increase using V-power over Shell95

Frozennova · 11 Nov 2011 at 18:30

Ivyforce said:
Which magazine did an article on super fuels back in'09.

They tested unl and super on a golf and focus.
Golf responded well to the super fuels.

2.1% power increase using tesco super over Tesco95
5.3% power increase using V-power over Shell95

I saw ~10% increase compared to the quoted 55bhp. This is on an engine doing 110k miles that is 22 years old. So not the golf they would have used in the tests.

Muffin` · 11 Nov 2011 at 18:31

SlyReaper said:
what do you gain from paying more for higher octane fuel?

Smugness, my high horse deserves better than that council estate fuel!

Alibaba99 · 11 Nov 2011 at 18:33

Peerzy said:
I don't use V Power, I simply realise I need petrol, pull up at the nearest petrol station and fill up with whatever petrol they offer at the most expensive price - is this much different to religiously using V Power (Which I'm under the impression is one single brand of expensive petrol and nothing more)?

V Power and Tesco Ultimate are both 99 octane, whilst most other supers are only 97.

VinceB1 said:
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?

The Americans use a different system to differentiate their fuels. 93 over there is equivalent to 98 here.

Maccy said:
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!

That's a 16% increase. Unless your car is running on the det limit whilst cruising (unlikely) that would suggest a 16% increase in the fuels calorific value and everyone using super would also get massive increases, which just doesn't happen.