Which Petrol?

[hodroyd]

Yes have bought in the states, but most cars only do around 70 anyway top wack, so it does not matter..!! I'll try some 100..!!

 

[drewf]

The point being, that you can run a Maserati in America, on the fuel available there, with no ill effects.

 

[hodroyd]

They do have Super and a load of other stuff of course, but you are right and they are obviously tuned to accomodate..!!

 

[CliveP1]

didn't watchdog or one of those consumer programmes say there was no difference in the quality of fuels and one car preformed better on normal fuel.

 

[CatmanV2]

Why are some cars designed to run on a minimum 98 RON then? Some cars do have the ability to deal with the knock using very clever methods and adjusting timing on the fly without any degradation of performance.

Of course they do, but what we're talking about is the difference in a car which can run on 95 being run on 98 and above.

Higher octane allows higher compression and higher theoretical efficiency.

C

 

[CatmanV2]

experimenter effect in action

Bang on

I'll experience what I expect to experience, even if I'm not sure what that is


C

 

[CatmanV2]

Evo magazine did a test on a Golf GTi

<snip>
The next test they did was on an E60 M5 and the results are interesting.

See, the problem there is simply summed up in those two sentences. *One* car in each case. Not even a control, let alone a statiscally valid sample. But it *is* your choice. It makes you happy

C

 

[CatmanV2]

General concensus then is higher octane gives you more power, but for Mr.C, we can't prove it, but if it works don't fix it..!!

No, the problem is there is no consensus. There's just as much stuff out there saying 'I tried it, it doesn't work'

Newton is (as ever) a special case. He retuned to use the additional Octane. If the ECU can adjust that much, then I'd expect some improvement. Not as much as he reports, but again, it's a (another ) single case

C

 

[CatmanV2]

didn't watchdog or one of those consumer programmes say there was no difference in the quality of fuels and one car preformed better on normal fuel.

They did, but their tests were no better than any of the other ones showing an improvement.

C

 

[CatmanV2]

Doesn't it say that in virtually every petrol car sold in Europe? That's the most commonly available petrol, so I'm certain they are factory tuned to deal with that fuel.

Indeed, the same as the maps tend to the rich so that you can take them to (for example) Andorra, and not have them blow up due to running lean.

C

 

[drewf]

Indeed, the same as the maps tend to the rich so that you can take them to (for example) Andorra, and not have them blow up due to running lean.

C

I've agreed with every other point you've made on this thread, but this one is back-to-front. You need to run leaner in the mountains, not richer. It's all about getting the correct air/fuel ratio. That's why we lean the mixture in a piston engined aircraft as altitude increases.

Also, compression ratio isn't the only reason for running high Octane - the Avgas rating is 100/130LL (there are two ratings for the same fuel, as one is measured lean, and one rich... more to do with forced induction and N/A engines really).

 

[CatmanV2]

I've agreed with every other point you've made on this thread, but this one is back-to-front. You need to run leaner in the mountains, not richer. It's all about getting the correct air/fuel ratio. That's why we lean the mixture in a piston engined aircraft as altitude increases.

Also, compression ratio isn't the only reason for running high Octane - the Avgas rating is 100/130LL (there are two ratings for the same fuel, as one is measured lean, and one rich... more to do with forced induction and N/A engines really).

*Doh* Of course. I've never really thought about that!

So why do they run the maps rich, do you think? Simply to avoid any risk of damage?

Immediate googling fails to answer: What are the other reasons for looking at higher octane?

C

 

[hodroyd]

This could go on and on and no matter how many cars are tested and show an improvement, eventually it's up the individual to put whatever they like in their tank, be it good, or bad, it's a choice we all make..!!

 

[drewf]

Yes - they run rich to avoid pinking in really hot countries and when the fuel is particularly poor.

The Octane rating in Avgas is also a by-product of getting enough lead-substitute material in to prevent valve wear on the engine, which might not otherwise really need such a high fuel RON rating.

You can't use 100LL (Low Lead) in a car engine with cats, as although it says it's low lead, it still contains about four times that of the old 4-star leaded fuel!

 

[hodroyd]

Steer well away from that then..??

 

[CatmanV2]

Gotcha, Drew. So the purpose of the *octane* is still to get higher compression. Avgas tends to have a higher octane because of the requirement to stop the valves from wearing? True?

@Rob. It would be quite simple. If the oil companies genuinely believed that there was a benefit, the could take a statistically significant sample of cars, and run some controlled tests that show a suitable improvement.
The fact that they don't, and couch their claims in marketing vagueness while relying on people to project their own desires speaks (in my opinion) volumes.
What *I* think it shows is that they *have* run the tests, and the know full bloody well that the improvements are nothing like what people want to think they are, so the simply don't publish them, CF 'Healthy' food, and , sadly, a lot of drug trials.

Your mileage may vary, and I'm doing this in good faith, so no insult or offence is intended to anyone. If anyone wants to discuss the concepts involved over copious beer, I'm happy to pay my share
C

 

[Contigo]

As I have said before if the car is designed to run on SUL then do it. If the handbook states that it should run in minimum 95 RON then so be it. We could debate this one all day long!

 

[hodroyd]

I run a Supercar and prefer to fill it with Super Fuel, I think it is better for the engine, I think it improves performance overall..!! Probably why such as F1 etc don't use 2 star..??

 

[drewf]

Until recently, they barely used petrol! There have been some extremely exotic mixtures used...

 

[hodroyd]

I agree, but they use exotic stuff, instead of cheap fuel for a reason..!!