Would my boring, ordinary car perform better or be more economical on the modern equivalent of Five-Star? Just curious, with a >500-mile journey on Mway and A9 coming up.

No, it’s a con it has no effect on your systematic.

You should be able to see old 5th gear tests on YouTube. For normal engines, no. For modern performance engines, you might gain a couple of hp.

No. Just think it out.

Nope Asda Petrol is fine…maybe (not a petrol head – just what i heard).

Well I understand how engines and timing used to work. It seemed worth asking if modern electronics could adjust to get more out of it.

No, it won’t.

Some engines are designed to run on higher octane (higher compression ratio), then the electronics adjusts the timing to make it work on lower octane, but with reduced power. If your engine is designed to work on lower octane in the first place, there’s nothing the computer can do to get more power out of higher octane.

Octane rating indicates the resistance to spontaneous combustion. Higher compression ratio means more power, and higher octane fuel enables this – rather than the fuel itself giving the extra power.

You have to have a modern engine where the ignition system can take advantage of the additional octanes. But it is real and measurable if you have a modern enough engine, but not necessarily noticeable.

I used to use it with my old 944 turbo, not because it generated more power or better economy (it didn’t do either), but it had better knock resistance so was ultimately safer for a 20-odd year old turbocharged engine. But obviously it’s like most things where it comes to engines – they’re only as good as the weakest link, so don’t expect higher octane fuel to fix problems due to poor maintenance or an engine in poor condition.

Thanks all.

summed up nicely by the mash

😀

Being in Canada I have a choice of really low Octane fuels 😀

So what I can tell you is that get noticeably better fuel economy (1l+/100km) out of 93 Octane when compared to 87 in a 2007 Mitsubishi.

Thanks for that, binners. I shan’t try drinking it.

I do wonder if the cleaning stuff may help, however it’s more expensive than just chucking red-X through every now and again, and the MPG benefit people have told me of is less than the cost differential.

You have to have a modern high performance engine

Or maybe turbo charged.. a bog standard engine won’t make a difference.

I once filled up a hire 1.6 Astra with super unleaded – the engine exploded on the outside lane of the M1.

I’m not sure whether that was related.

Thinking about, my own Astra (mkII GTE 8v for nostalgia) also exploded in a fire ball a few years later at the bottom of Haldon Hill.

Maybe Astras are just prone to blowing up?

I’m pretty sure I’ve provided a valuable contribution to this thread.

I once filled up a hire 1.6 Astra with super unleaded – the engine exploded on the outside lane of the M1.

1.6L diesels will do that.

(-:

drive at below 55-60 mph.

The Daily Mash really have a bee in their bonnet about it

The ecu will allow your car run on a huge range of fuel from utter shite to avgas. It will run not necessarily very well but run.
If you have it remapped to only run on the high octane super fuels you will gain some more power.
How much depends on the car, as ever turbos have a lot more to give. A normal aspirated small engines – you’ll engine to send quite a bit to see a marginal gain.

How common is it for an engine to be able to adapt to it, these days? It used to be pretty scarce, rapid turbo stuff and the like but cars are pretty damn clever now… I suppose all you really need is a knock sensor and a bit of timing control.

I accidentally overtuned my motorbike so it could only run safely on super, that was annoying.

Modern cars have a closed loop control between the knock sensor and ignition, so the engine is always pushing the ignition to the limit, pulling it back as the knock sensor detects the onset of knock. So you increase the octane of your fuel you can push your ignition more, and that can translate in more power if you’re pushing the engine, or better economy if you’re just pootling along. Its a fairly basic feature of modern engines these days and would have thought standard feature for any engine manufactured in the last 10 years.

Should I use the expensive stuff on my 1978 motorbike?

Is it turbo charged?

Nope. Honda gl1000

If you’ve got an Japanesse import (as is imported from Japan after purchase not a UK/EU spec Jap car) it’ll likely run a bit smoother and make a bit more power on 99ron fuel as that more the standard in Japan I’m told. It’s supposedly the reason why JDM cars are power rated a bit higher than their export versions, it’s nothing to do with them keeping the ‘best’ engines for themselves.

Nope. Honda gl1000

Poor bugger, it’ll probably be pining for 5 star with a lovely bit of lead on top…

P-Jay
If you’ve got an Japanesse import (as is imported from Japan after purchase not a UK/EU spec Jap car) it’ll likely run a bit smoother and make a bit more power on 99ron fuel as that more the standard in Japan I’m told. It’s supposedly the reason why JDM cars are power rated a bit higher than their export versions, it’s nothing to do with them keeping the ‘best’ engines for themselves.

If it’s an older turbo charged car it’ll either be mapped for one or tother.

It’s odd.

My old petrol bimmer always returned less MPG with posh petrol.

My diesel bimmer does the same with posh diesel. Why?

Because they can advance or reduce the engine timing on the fly depedning on the fuel. At least the petrol ones can or so I’m told, so I presume the dirty tractors can do the same.

My diesel bimmer does the same with posh diesel. Why?

Completely different thing for diesels. Posh diesel has high cetane rating, which indicates how easily it burns under compression, the opposite of octane rating for petrol.

So higher cetane = smoother running, better starting and better combustion in any diesel engine.

Over the last 10k+ miles or so in my van I have tried to stick to using 4 types of diesel. Regular Shell or Esso, Shell V-Power Nitro+ or Esso Supreme. I really can’t notice any performance difference between them, but with 170bhp+ on tap I’m rarely pushing the limits of the available power. What I have found though is that the regular diesel and the Shell V-Power all seem to give similar MPG (27.5 to 30.5), but the Esso Supreme is giving better MPG (30.0 to 32.0). Each MPG measurement is taken over at least half a tank before being brimmed again, more usually over 3/4+ of a tank before filling. Driving is a mix of long runs, motorway, local pootling, and over the course of the 10k+ miles probably averages out.

As above, if your modern car has a fancy ecu that will fuel-learn and adjust the timing on the fly, you may get a few more mpg or a few more horsepower, depending on how you drive it.

Higher octane stuff can help keep your injectors nice and clean too. I usually do a tank full every few thousand miles for this purpose.

I also use it in the classic car: some of the higher octane offerings have no biofuel in them. This reduces moisture absorption into the fuel, and reduces mould growth in tanks, filters and lines in cars left sitting for long periods. I’ve seen some really horrific mould growth on fuel senders in classics run on normal pump fuel containing 5-10% biofuel.

So it’s worth it in diesels? Specifically, 2004 VW 1.9tdi?

I remember an Evo test they did a while ago on different cars.

If I remember rightly it only made a difference on turbo cars (they could sense the fuel and adapt)

Not sure if they did any diesels, but perhaps the presence of a turbo on nearly all diesels means it is worth a go?

I’ve recently started the habit of running a tank of Shell Premium Diesel every few thousands miles as I think it’s a good idea for the cleaning benefits and probably more effective and better engineered than pouring an additive into the tank. Hopefully that’ll keep things like injectors and the DPF running cleaner for longer.

I have noticed a performance difference when running higher octane fuel in motorbikes on track days but that’s in an environment where a few more bhp on a long straight at over 150mph will be noticeable and I think it also protects the engine better for that kind of use. I’ve never noticed a difference on the public road.

I feed my Motorbikes on the posh stuff, but they’re old two stroke sports bikes, so anything that will reduce the chance of detonation is worth the money! As well as having less ethanol to bugger up tanks/fuel lines.

So it’s worth it in diesels?

It’s worth trying it out – it’s not limited to performance engines with diesel. In my experience the cars run better and give some increased economy, but not enough to justify the cost on economy alone.

Total diesel also seems to be better. And Shell basic diesel smells like it has cetane improver in it.

I’m pretty sure most Japanese bikes were designed to run on boggo unleaded from the mid-late 70s.

If your car or bike can take advantage of the higher octane fuel whether it’s through fancy-dan electrickery, or accidentally having made the compression ratio too high or the timing too advanced to be able to use the cheap stuff without it blowing up then there’ll be a performance advantage. If not, there won’t, and it’ll be slower because the higher octane fuel doesn’t burn as quickly, therefore the expansion of the gases happens at the wrong time in the piston stroke (or rotor for all you Wankels!) to get the most out of it.

So probably no, but possibly yes 😀

Super unleaded and Avgas smell a bit nicer too.

It’ll probably say in the manual.

My FiL’s new Volvo XC70 said it wanted 91 but would work with 87 (US numbers).

I’m probably not the best person to ask, but – fire away…