99+ octane unleaded not that popular nowadays or is it??

[Bobby Dazzler]

£2.42 a litre!

In 2006! Not sure what regular unleaded cost. Maybe not so different from today.

 

[clk320x]

In 2006! Not sure what regular unleaded cost. Maybe not so different from today.

In February 2006, the average cost of 95 RON was 90p/litre.

Just over 60p/litre was tax!!!!!!

 

[Colesy]

So what's the consensus, is the higher octane fuel better or worse for the engine?
I use 97 RON in the Merc as a general rule, but put 99RON V power in my 1200cc motorcycle the other day.

 

[DSM10000]

So what's the consensus, is the higher octane fuel better or worse for the engine?
I use 97 RON in the Merc as a general rule, but put 99RON V power in my 1200cc motorcycle the other day.

It cannot cause damage to the engine but unless the engine is designed to take advantage of the higher octane via higher compression, ECU mapping etc there will be no benefit

 

[BTB 500]

Generally 'premium' fuels have a better additives package (cleaners, friction reducers, etc) as well as the higher octane rating, but of course they cost more so whether they are 'worth it' or not is still a personal call.

 

[Yugguy]

I thought, simplistically, that higher octane meant a bigger bang, the ecu would adjust and you'd get more power?

 

[400ixl]

Not necessarily. The ignition gets advanced for higher octane fuels and retarded for pre-ignition in lower octane via the use of a knock sensor, Most manufacturers only have a limited range and they set it for the most common fuel for that region. So if the fuel takes it outside of that range then there will only be a limited advance compared to optimal and only a partial use of the different fuel.

 

[DSM10000]

I thought, simplistically, that higher octane meant a bigger bang, the ecu would adjust and you'd get more power?

Octane rating is only a measure of resistance to pre-ignition nothing more. It does not reflect the energy density of the fuel.

Put ordinary pump petrol in a Formula one car and it will run poorly with lower power, use the fuels used in F1 in a road car designed for 95 octane and it will not give power increase unless the ECU map is programmed to detect and allow for changes but an ECU cannot change the compression ratio

 

[Yugguy]

So I guess it's not worth sticking super in the wife's 1.0 Fiesta?

I remember when I had my 172 though, it was mapped from factory to run on 97, not 95.

 

[Riva811]

Interestingly tesco fuel makes my car accelerate badly, BP 97 makes a massive difference. Perhaps it is a dodgy station

Sent from my H8116 using Tapatalk

 

[Bobby Dazzler]

Interestingly tesco fuel makes my car accelerate badly, BP 97 makes a massive difference. Perhaps it is a dodgy station

Sent from my H8116 using Tapatalk

Or nocebo effect.

 

[clk320x]

So I guess it's not worth sticking super in the wife's 1.0 Fiesta?

Better additives in the premium stuff so it’s not a complete waste.

 

[markjay]

So I guess it's not worth sticking super in the wife's 1.0 Fiesta?

I remember when I had my 172 though, it was mapped from factory to run on 97, not 95.

Any car new or old, big or small, will benefit from the additives included with the premium fuels.

The higher Octane though will only benefit cars with highly-tuned sports engines.

 

[GeeJayW]

Just me being pendantic (again perhaps):

Pre-ignition is uncontrolled combustion that occurs before the spark event (hence the name) that produces very high combustion pressure spikes. It is caused by a hot spot in the combustion chamber or by a spark-plug that has the wrong temperature rating (too hot) and is not controlled by fuel octane quality or by retarding the ignition timing. Left unchecked, pre-ignition can be very destructive and it's not uncommon to result in the piston crown failing catastrophically. The very high cylinder pressures can also split pistons and damage the crank bearings. Very nasty..

Detonation, knock or pinking is the sound caused by uncontrolled explosions that occurs in the end-gases after the spark event, but ahead of the main flame front. Higher octane quality, retarding ignition timing (via a knock sensor) and optimised combustion chamber design all help to control, even eliminate detonation. In most cases engines can tolerate some amount of knock without significant damage. However if severe knock is left unchecked, the continued disruption to the boundary layer protecting the combustion space can result in hot-spots forming which can the lead to pre-ignition. So it is best to avoid detonation where possible. If an engine is calibrated for high octane fuel, then running on regular fuel will cause the engine to retard the ignition timing in order to avoid going into knock. Doing this for the long term is not good as it pushes up exhaust valve temperature and places too much reliance on the (£50) knock sensor to protect the (£5k) engine.

Many standard modern petrol engines (not necessarily highly tuned ones) have some 'headroom' when it comes to spark timing and can take advantage of higher octane quality. However, the power/performance benefits are subtle. I have in the past measured the benefits of such fuels using engine and chassis dynamometers, so know first hand that there are benefits to be had. It's not so easy using your backside dyno.

Premium fuels either have different (more expensive, more advanced) additives or simply more additives (higher treat rate) than regular fuels. They do a better job of cleaning the injectors and inlet valves.

Some premium fuels achieve higher octane rating by the inclusion of Ethanol (which contains oxygen, which is not a fuel), whilst others are formulated with high octane hydrocarbon components such as toluene.

Formula 1 fuels must be 99% formulated from components found in commercial forecourt fuels. The main difference is the F1 engines never do a cold start, so they don't need as much (if any) of the lighter 'front-end' components. Before the present boosted-Hybrid configuration, I know of at least one F1 car that ran perfectly well on forecourt premium fuel.

As mentioned already, the choice to use premium fuel is a personal one unless of course it is specified by the OEM.

Sorry for going on, just thought I'd share some detail...

 

[Felstmiester]

GeejayW. Jesus!! What do you do for a job?? You obviously know your stuff.

Back in the day when I had the cosworth there would be a lot of talk about detonation. At the time we was getting 450+bhp and I remember the big tuners would drill and tap a fitting into the inlet plenum so they could tap into it with a small hose linked into a set of ear defenders so they could hear the point of detonation. This was all linked in with live mapping. I’m sure things have come on a long way by now but at the time it was the only way I guess. If my memory serves me correct it was around the same time they was phasing out 4 star fuel and bringing in normal unleaded.

Food for thought though. All those years ago the 2ltr pinto with a little help from an extra cam and forced induction was able to produce 450+bhp with not a great deal of money. I remember I had a little foam lined box with 4 different chips. Pop the lid out on the dash, pull the ecu out, take the top of, unplug and replace with the one of your choice lol. I remember I had one with a label saying big flames.

 

[GeeJayW]

I'm retired. Spent more than 25-years as an automotive engineer working in R&D for one of the major oil companies, mainly developing fuels, but some engine lubricant products as well.

 

[Eddie01]

Quite possibly. Maybe. Not sure. It was a long time ago!

DSM10000 mentions BP 102 RON which sounds about right. A little Googling suggests the petrol station might have been Chicheley Park Connect in Newport Pagnell, or Wavendon Gate Connect in Milton Keynes.

Source: BP launches 'UK's highest-octane fuel' | Autocar

You’re correct, I used to fill up my jerrycans there and drive to POD, they stopped selling it many years ago so I end d up blending my own with C16 and V Power,

 

[RickMM]

I'm retired. Spent more than 25-years as an automotive engineer working in R&D for one of the major oil companies, mainly developing fuels, but some engine lubricant products as well.

Not wanting to thread-jack (and I appreciate this is not specifically AMG related), but I was wondering whether you'd have an opinion on using modern synthetic oils in older vehicles. I'm thinking particularly of 1970/80s motorbikes, where a lot of "internet experts" claim that fully synthetic oils shouldn't be used for one reason or another. Some claim that synth oils "attract" more moisture if a historic vehicle left unused for a while. Is there any truth in that?

Just a couple of many thread examples, one 4-stroke and one 2-stroke application

Engine oil - Z1OwnersClub GB

kh400 oil

 

[GeeJayW]

Not wanting to thread-jack (and I appreciate this is not specifically AMG related), but I was wondering whether you'd have an opinion on using modern synthetic oils in older vehicles. I'm thinking particularly of 1970/80s motorbikes, where a lot of "internet experts" claim that fully synthetic oils shouldn't be used for one reason or another. Some claim that synth oils "attract" more moisture if a historic vehicle left unused for a while. Is there any truth in that?

Just a couple of many thread examples, one 4-stroke and one 2-stroke application

Engine oil - Z1OwnersClub GB

kh400 oil

There are a number of potential areas where modern engines differ somewhat from historical ones, e.g. elastomers used in seals, bearing materials, surface treatments, clearances, and so on. In the meantime not only have the base oil technologies changed, but also the additive technologies. Modern oils are typically much lower viscosity, so in the past a good old 20W-50 would be just the ticket. Today 0W-30 oils are not uncommon and while they offer the appropriate cold start protection for modern engine designs, I'd be less comfortable with a legacy application like 70s/80's motorbike engines.

It's also worth pointing out that there are different types of synthetic base oil and many different formulations of additive technologies.

I suggest you start a new thread to discuss further. You may get more input from others.

 

[kit17]

On my 2017 c63, it states 98 or higher, sometimes I use BP super which is 97. Does it really matter that it’s only 97 ? What’s people’s thoughts?