High octane petrol

[hayfield]

 A simple question, is it worth paying the extra please.

 

If so do you use it all the time or every now and then ?

[dhjgreen]

6 minutes ago, hayfield said:

 A simple question, is it worth paying the extra please.

 

If so do you use it all the time or every now and then ?

Depends on the car.  I had a '97 Volvo that was a bit gutless, the petrol made a big difference at the time.

[jonhall]

Assuming you aren't talking about the 106 octane that BP only sell down the road from Silverstone etc..

 

Last time I read up on the subject, the general thinking seemed to be the 98octane 'better' petrol was only worthwhile in older/less highly tuned engines, and it was more about the cleanliness of burn reducing deposits in cylinders and around valves. Ironically the sort of car whos' owners are less likely to spend the extra.

 

The 'performance' cars tested seemed just as happy on either, although it was a very small sample size.

 

My turbocharged Subaru runs the cheap stuff, not least because of the quantity it gets through!

 

As a general point, when I was still at school the chemistry students were taken to BP's research labs at Sunbury, and I saw engines running on test rigs that looked at this sort of difference. Whilst I don't know about petrol, I went on to practice R&D in an industry that often gets asked 'is product X really better than the cheap own brand?' and I can observe, yes, the reason my employer pays hundreds of people and invests millions of dollars, to prove it, if that wasn't the case, they wouldn't spend that money, and in my experience its our competitors who will complain to the likes of the ASA if they think we can't support that data. I assume that the fuel industry is pretty similar, and that the scientists can demonstrate the difference is measurable.

 

Jon

 

[Gwiwer]

As I understand it the premium fuel is only worth paying for if you drive a much older car for which the higher octane means significantly better performance or if you are one of the select group of folk who (legally  ) own a high-performance modern vehicle which does indeed run better on high-octane fuel.  

 

For everyone else standard unleaded is fine since for many years now nearly all car engines have been built around the fuel supply rather than vice versa.

 

When the UK first defined octane ratings in fuel we had one-star up to five-star and many manufacturers recommended the requisite for their models.  Three-star was the norm with four-star for larger-capacity engines requiring a little more oomph.  You seldom if ever saw one-star, two-star was blended into two-stroke and five-star was for the premium-category few.  We have over time come to the point where we effectively have only 3 and 4-star fuels; there was little or no real need for the others and commercially they made insufficient sense to offer at the pump.  

 

A tiny amount of specialised fuels remains available such as those used specifically for motor-racing purposes and are not generally available to Joe or Joanne Public.  

[chris p bacon]

No 1 son has a VW Schirroco which says it should run on 'superunleaded' he's put some ordinary unleaded in on a couple of occasions and says it runs like a gutless pig.

[simontaylor484]

I only have experience of diesel over the last 10 years. I got more mileage from the premium diesel than supermarket diesel but not as much more than normal brand diesel. 

I only used the premium diesel as a fill every  4 fills instead of putting redex in

[alastairq]

There is a lot of misinformation circulating round the hoi-polloi regarding fuels, octanes and stuffs.

 

Especially now we are joining the rest of the uncivilised world, and introducing more in the way of alcohol [ethanol] into our fuels.

 

Octane rating itself is nearly all linked to the compression ratios in older motors, and timing [to a degree!] in new cars...It's all to do with detonation.

 

If a cylinder has a high comp ratio, or is a bit coked up [which has the same effect] then the fuel can ignite before it is supposed to, eventually leading to damage [pinking].  The answer is, to use a higher octane fuel. [Or, decoke the engine?]

 

Modern motors which are completely controlled by engine management computers [what do drivers actually do with themselves in todays cars, anyway??}, automatically adapt to a new fuel, but it does take a bit of time for the ECU to sort itself out.

 

As an old car driver/owner, I have lived through the 'leaded/unleaded' debacle, now we have the 'ethanol' fear mongering.

 

I know many old car owners whose engines were designed to run on, effectively, what was 'pool' petrol, claim immense improvements by splashing out on the very best fuel their pennies can buy!  [Often , poor running's down to poor servicing & tune]

 

The 'public' can also buy petrol [delivered to your door in drums] that completely replicates the consist of petrol that was sold in the 1960's and 70's.....which today's petrol bears no relation to, in terms of what it is made of. [Several brands, actually, some sold to owners of garden machinery intent on storing over winter. Sunoco Optima98 is one, supposedly has a 'shelf life' of 3 years.  Todays 95 octane U/L fuel has a shelf life of around a month or so! High volatility of head end components means it evaporates before your very eyes...]

There is also a 'difference' in components between 'summer' petrol, and 'winter' petrol..[and bits in between as well!].  Winter petrol has  a higher volatility so that starting isn't an issue in the cold weather.  Which is why one should really buy ones fuel from a retailer with a high turnover....so one doesn't get 'winter' fuel that has sat in the tanks, come May!   

 

For those who may be interested, Manchester University conducted a shed load of scientific tests on an old engine.....trying to find out why old technology engines [40's, 50's, 60's] had problems running on today's fuel? When they didn't have issues, back in the day?

The lead on this series of tests was [Dr?} Paul Ireland, known in ancient MG circles.

https://www.veloce.co.uk/store/Classic-Engines-Modern-Fuel-The-Problems-the-Solutions-p151478624

 

[The book can be found cheaper esewhere]

 

He also runs a website with a Q&A facility.

 

His book covers the entire experiment, and details chapter & verse on the entire test results...

 

He also found that higher percentages of ethanol [E10 is what we shall see soon] actually makes old designs of engine run very much better.

 

The issues with ethanol mainly centre on the fuel system itself, and ethanol's proclivity for being sucked out of the petrol when there's a presence of water.

the fuel system issue really shouldn't exist in the first place, if proper maintenance and replacements in an old car's fuel system have been conducted over its lifetime. But, so many owners of old vehicles try & rely on materials that were used originally [possibly still original] for gaskets, hoses and rubber stuff...which gets eaten by ethanol. Odd, in my eyes, really, since todays ordinary cheapo pump fuels are nothing like the stuff sold 50 years ago!! So why rely on original fuel system components?

 

 

[Quarryscapes]

Everything for the UK market since 1992 will adapt itself to run on the good stuff, but you will very rarely notice the effects. Engines with carburettors may run better, but it'll be a bit of a fluke really unless it has been specifically tuned to use high octane fuel. EFI engines without Catalysts fit into the same category as Carburettors. 

[Bernard Lamb]

Takes me back to the early 1960s.

The testing lab was just down the road and I was actually offered a job there.

The racket was to find a batch of petrol that was only just below the bottom limit of the higher grade. The cert was marked and this fuel was sent to a garage that had around half a tank of the genuine higher octane fuel. Mix the two together and sell it at the higher price.  If checked it would pass the test. It needed several outlets and drivers in on the fiddle for it to work. Plus of course the lab rat. It was made quite clear to me what was involved in the job and I turned it down. I believe it was several years before those involved were caught.

Bernard

[alastairq]

LPG fuel has a slightly higher  octane rating than the old 5 star. Thus it is pretty much essential if one intends to run one's Aston Martin V8 on the school run.

 

23 minutes ago, Quarryscapes said:

everything for the UK market since 1992 will adapt itself to run on the good stuff

 As far as I can determine, Daihatsu sold the 4Trak Indy right up until the turn of this century, { in the UK} but it doesn't/didn't have any form of ECU or electronic engine control.

Thus, like the older Peugeot diesels, it can run on anything that might conceivably go bang.

I unintentionally popped 25 litres of petrol in mine a couple of years ago or so [In Dorset, so I might be forgiven?}

Normally such a 'mistake' would cost a modern diesel engined vehicle a shed load of money to rectify. Not so the 4Trak, which happily chugged of into the Dorset sunset  without a murmur....Not ideal though, although petrol was some nearly 10 pence a litre cheaper than diesel at the time...

I believe Dorset has now recovered from my visits..?

Edited May 19, 2021 by alastairq

[Nearholmer]

11 minutes ago, alastairq said:

He also found that higher percentages of ethanol [E10 is what we shall see soon] actually makes old designs of engine run very much better.

 

 

Not sure what "old designs" means in terms of dates in this context, but I'm "into" pre-WW1 internal combustion engined locomotives, and the sort of low-revving, low-compression, spark-ignition engines that most of them used were specifically designed to run on anything from pure alcohol (ethanol or methanol*), through "light petrol" (what we would call "lighter fluid" now), to "heavy petrol", which SFAIA was something close to what we recognise as petrol today, and the manuals for them gave carburettor and other settings to suit various fuels.

 

There are several contemporary journal articles raving about how good a fuel alcohol was for these engines, clean-burning, smooth-running, less burning of valve-seats etc, and in Germany it was very widely used, much more so than in the UK, I think because it was legal to distil it without a license, and there was no duty payable on it. IIRC it gave a slightly lower power output than contemporary petrols, but that sacrifice was considered worthwhile.

 

At that stage, the fuel systems were (a) very simple, and (b) made from copper piping. Gaskets were probably still copper, or simple compounds of asbestos, too. What I don't know is how they coped with moisture contamination, alcohol being very hygroscopic - possibly they just made sure it was "fresh".

 

*In the foresty industry, locos were fueled with locally distilled wood alcohol, which must surely have involved poisoning a few people along the way!

 

Apologies for going way off-topic. Getting back on-topic, I would think that the only modern engines that would benefit from abnormally high octane levels would be those with abnormally high compression ratios.

[Quarryscapes]

14 minutes ago, alastairq said:

LPG fuel has a slightly higher  octane rating than the old 5 star. Thus it is pretty much essential if one intends to run one's Aston Martin V8 on the school run.

 

 As far as I can determine, Daihatsu sold the 4Trak Indy right up until the turn of this century, { in the UK} but it doesn't/didn't have any form of ECU or electronic engine control.

Thus, like the older Peugeot diesels, it can run on anything that might conceivably go bang.

I unintentionally popped 25 litres of petrol in mine a couple of years ago or so [In Dorset, so I might be forgiven?}

Normally such a 'mistake' would cost a modern diesel engined vehicle a shed load of money to rectify. Not so the 4Trak, which happily chugged of into the Dorset sunset  without a murmur....Not ideal though, although petrol was some nearly 10 pence a litre cheaper than diesel at the time...

I believe Dorset has now recovered from my visits..?

 

We were talking about petrol 

[alastairq]

16 minutes ago, Quarryscapes said:

 

We were talking about petrol 

 So was I, albeit, inadvertently

[AndrueC]

Many years ago when I owned a Nissan Sunny with a 12 valve engine (the last before ECUs and Catalytic converters arrived) I felt that it had a bit more pep on high octane fuel and seemed more economical but neither was sufficient to justify the extra cost. Sunnys weren't as slow as people liked to claim at the time but even so 'more pep' was very much a relative description

 

Since then I've tried it in different 'bog standard' vehicles with no obvious benefit. I think that modern injection engines with ECUs render it pointless unless they have actually been designed to for it.

[Kris]

I have on a few occasions put in the "high octane" petrol as it is recommended for the car particularly if driving "spiritedly". I don't notice any difference in the amount of power but I did get a few more mpg. This however was not enough to justify the cost, that alongside the fact that super unleaded is not sold locally means that I don't bother purchasing it. 

Edited May 19, 2021 by Kris

[57xx]

6 hours ago, Kris said:

I have on a few occasions put in the "high octane" petrol as it is recommended for the car particularly if driving "spiritedly". I don't notice any difference in the amount of power but I did get a few more mpg. This however was not enough to justify the cost, that alongside the fact that super unleaded is not sold locally means that I don't bother purchasing it. 

 

I ran my car on Super unleaded for a while as it was not getting good MPG on regular. I too notice a slight boost in MPG with it, though noticing any power difference was a lot harder as I wasn't booting it WOT everywhere. In the end I just switched back to regular unleaded.

 

In contrast, the highest octane I've every run was 124RON - in the race bike. It was about £5 per litre but so worth it.

[Kickstart]

Firstly, by “high octane” do you mean Shell vPower and the like, or fuels with just a higher octane rating.

 

The posh fuels have various claims of better additive packages (whether better detergents, more power, etc) as well as the higher octane rating. These additives alone might help.

 

But most cars and bikes will be unable to take advantage of higher octane fuels. Knock sensors are far from universal. And even if fitted the ecu might well not be mapped to take advantage of higher octane fuel. Engines with no feedback at all will gain nothing from higher octane fuel, unless they have been manually adjusted to suit in which case engine damage would be a risk if filled with normal unleaded. The adjustment might be easy - the Bosch Motronic system in my old Alfa 33 could be switched from 95 to 98 octane fuel by swapping a “relay shaped device”, which just changed which pairs of 4 wires were connected.

 

A few years ago I had a play and ran my MX5 on Shell vPower for a month. At the time I was keeping a fairly close eye on fuel consumption. It gave no improvement on fuel consumption (actually used very slightly more, but within experimental error range). No noticeable change in performance. Subjectively the engine felt slightly smoother.

 

Our old Maserati 222 (built 1989) has noticeably better performance on higher octane fuel. But it does have a knock sensor with feedback to the ecu, and can adjust boost to take advantage of it.

 

All the best

 

Katy

[hayfield]

Its the choice at the Petrol pumps 97 verses 99 with added chemicals, not race fuel

[Michael Hodgson]

What octane is used chip fat then ?

[alastairq]

1 hour ago, hayfield said:

not race fuel

 That really is a bit of a misnomer actually.

So-called 'race fuel' seems to be an ism that covers any fuel not sold directly via pumps.  

In fact, one can still purchase leaded fuel, or even fuel made with the same components that made up petrol back in the 1960's. 

Some of these so-called 'race' fuels are  sold to overcome the limitations of using today's pump petrol.

For example, shelf life?

As I mentioned above, shelf life affects the likes of gardeners, etc, who use petrol engined garden machinery, [strimmers, chain saws, mowers, etc.] Which are not used all year round. Ordinary pump petrol left to linger in fuel tanks actually goes 'off' after a month or so [loses volume as well].

 

 

 

[alastairq]

11 minutes ago, Michael Hodgson said:

What octane is used chip fat then ?

 Probably ITRO 25-40?   Similar to diesel? Or heating oil?   Adding dregs of local vodka bottles helps raise the octane rating  of chip fat, which is an undersirable trait.   

[Michael Hodgson]

15 minutes ago, alastairq said:

Adding dregs of local vodka bottles helps raise the octane rating  of chip fat, which is an undersirable trait.   

The car will be charged with drunken driving!

I can see Robocop breathalysing the car 

Edited May 20, 2021 by Michael Hodgson

[alastairq]

2 minutes ago, Michael Hodgson said:

The car will be charged with drunken driving!

I can see Robocop breathalysing the car 

 Shouldn't' this be linked to the self driving cars thread?

[tigerburnie]

21 hours ago, alastairq said:

LPG fuel has a slightly higher  octane rating than the old 5 star. Thus it is pretty much essential if one intends to run one's Aston Martin V8 on the school run.

 

 

My old V8 Aston ran on supermarket petrol but with an additive as it should be run on leaded 4 star, this was a mechanical fuel injected car, so it didn't have any mpg to worry about, I was lucky to get 10 mpg.

[Michael Hodgson]

8 hours ago, tigerburnie said:

My old V8 Aston ran on supermarket petrol but with an additive as it should be run on leaded 4 star, this was a mechanical fuel injected car, so it didn't have any mpg to worry about, I was lucky to get 10 mpg.

I remember a product called Redex, used to be pushed on every forecourt but I haven't seen it for years.  Never bothered with it myself.