Super Unleaded 98ron - wow!

LostKiwi

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I think anyone with a Terraclean franchise would disagree with you there ;)
I wonder why?

Actually just thinking there are some modern engines with significant carbon issues...
The direct injected petrol engines from BMW have serious issues with carbon build up in the inlet ports blocking them as there is no fuel wash effect on the ports (and the EGR doesnt help) but it doesn't manifest itself as a combustion chamber issue.
 

Uncle Benz

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Yeah, it does ;) Restricting the volume of air incoming messes with the stoich, and burning is inefficient, therefore more soot. Just sayin'
 

Monkey Wrench

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To get the effect your suggesting would mean significant carbon deposits. Modern fuels/engines are also far less prone to carbon build ups than days of old. I've had heads off newer cars that have done over 100k miles and the carbon levels were so low as not to be worth doing anything about.
Mines a Sunday driver so running costs are not my priority, I'm putting 98 in cos it's supposed to keep things a little less clogged? I sometimes put 98 in me '51 Rav for the same reason, keeps me happy...
 

matthew k

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I don't think we're ragging on the original poster, I may have miscalculated the cost differential, but it's around 8-10p per litre. There have been tests done on rolling roads, Fifth Gear did one, the difference was tiny, a couple of HP. 95 RON is quite high by the grand scheme of things, my w211 E55 performed pretty much the same on 95-99. Had it been modified with a smaller pulley/remap then maybe a greater difference would have been noticed.
 

LostKiwi

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Yeah, it does ;) Restricting the volume of air incoming messes with the stoich, and burning is inefficient, therefore more soot. Just sayin'
Maybe but the lambda feedback takes care of that until it gets out of spec then posts an EML.
 

Craiglxviii

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Now then, you all shout "placebo", but I don't see any science backing that up ;-)

Higher octane fuel is more resistant to pinking, or pinging to our American friends. Any car fitted with knock sensors will retard the timing if pinking is detected to protect the pistons from potentially damaging temperatures. On a new engine designed for 95 ron you will see no advantage running 98, but once some carbon has built up and an engine runs with hotter areas in the combustion chambers than when it was new it can be a different story. If timing is regularly being retarded by the ecu from knock detection then it will run better on 98 ron, as higher octane fuel is more resistant to knocking.

Just defending the OP, who might be feeling a bit low after mentioning it :)
I can give you the straight fact and data behind the testing if you like. The results across a wide range of OEMs, models and engines all point to placebo effect as being the massively overridingly main factor.
 

L John

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A medical test was done with a group of people taking placebo tablets VS a group taking tablets designed to treat a condition.
The groups didnt know whether they were getting the real deal or the placebo.
Many of the placebo group believed the pill to have a positive effect.... as expected with placebos.

The test was done again with new groups, but this time the placebo group were all told they were getting the placebo.
Maybe they thought they were being lied to, because just as many believed to have a positive effect from the pill despite it being a placebo and being informed about it.

The same group were then given a double 'dose' of placebo and even though they were told it was a double helping of placebo, the benefit from the tablets was increased significantly.

This is from a true test that I know about from my son, I don't have the figures but it makes sense in a strange way as people will believe what they want to believe even when they are told it absolutely has no effect.

Just the action of doing something different to influence a desired outcome, such as a football supporter wearing special socks to help their team win is very common.

So, placebo is real, it does work, and I believe the OP made his car go faster.
Not by the power of the extra octane but by the power of his mind.
 

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I'm sure Premium fuels are mostly nonsense. But has been said it's a personal choice, and if I had a car I really cared about and could afford to use them I probably would.
 

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Maybe they do make a difference?
 

L John

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We all know there is a tiny difference but that difference is not enough to notice with a butt dyno as the OP was suggesting, is it worth the extra was a question asked earlier.
On a lower compression engine the test would likely show a smaller difference.

BP unleaded vs BP Ultimate was the only tests done on the same brand.
The ultimate couldn't muster up a single extra pony for an extra 8p per litre.

P.S. I've stated that my bike runs better at low RPM using 98 RON even though it's not needed (post#6 on this thread).
The fuels have other differences too, it's not just a RON number.
 
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Craiglxviii

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The whole thing about placebo & mind over matter comes into its own with psychosomatic, that is the interaction between body and mind. A placebo drug can cause health improvements purely through the patient believing that it is working that way (and in doing so, increases white blood cell count, takes more exercise thus improving blood flow, eats more healthily thus reducing body fat etc). That’s quite well documented as is the reverse.

Where it’s man- machine interaction, then yes a placebo can indeed have you believing that the engine is more powerful, thus you’ll drive the car harder, brake later, theow it around more and generally take more risks- thus actually driving faster. It has zero effect on the performance of the car however.

On the maths of premium fuels though... 8ppl on my cars = £6/ tank or £0.02/ mile, which for my daily commute equals £500/ year. Decoking the engine costs say, £1500 and I’d expect that to be done every 200k or so, so unless one is doing 50k per year then burning premium fuels literally isn’t worth it.
 

oigle

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The whole thing about placebo & mind over matter comes into its own with psychosomatic, that is the interaction between body and mind. A placebo drug can cause health improvements purely through the patient believing that it is working that way (and in doing so, increases white blood cell count, takes more exercise thus improving blood flow, eats more healthily thus reducing body fat etc). That’s quite well documented as is the reverse.

Where it’s man- machine interaction, then yes a placebo can indeed have you believing that the engine is more powerful, thus you’ll drive the car harder, brake later, theow it around more and generally take more risks- thus actually driving faster. It has zero effect on the performance of the car however.

On the maths of premium fuels though... 8ppl on my cars = £6/ tank or £0.02/ mile, which for my daily commute equals £500/ year. Decoking the engine costs say, £1500 and I’d expect that to be done every 200k or so, so unless one is doing 50k per year then burning premium fuels literally isn’t worth it.


And that assumes a decoke isn't necessary when using premium fuel. Might delay it a bit is all really. Water injection is a lot cheaper and more effective as a decoke.
Some higher comp motors with knock sensor equipment will certainly do better on premium but, if the manufacturer suggests you use standard fuel, no benefits are available.
 

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Interesting discussions here even if I don't fully understand some of the posts.
 

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The main thing you all forget is about the ECU which is adaptive.....it all depends how you drive as well as the fuel?

As said back a bit the ECU will also adjust the ignition according to what fuel is being burnt also if the engine runs smoother then the combustion must be cleaner so therefore must give better performance even if it can`t be measured.

I use Shell Nitro Diesel with a ratio of 2T, it up`s the cetane rating a couple of numbers, and if i miss a dose out and just use Nitro the engine is noisier uses more fuel and has a rougher idle together with black smoke on acceleration.

When i fill up again and use the 2T it is like a different car to drive is so smooth and i would put it up against any petrol engine even when from cold........and is not a placebo effect otherwise i would not bother to use it.
 

Capra

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The main thing you all forget is about the ECU which is adaptive.....it all depends how you drive as well as the fuel?

As said back a bit the ECU will also adjust the ignition according to what fuel is being burnt also if the engine runs smoother then the combustion must be cleaner so therefore must give better performance even if it can`t be measured.

I use Shell Nitro Diesel with a ratio of 2T, it up`s the cetane rating a couple of numbers, and if i miss a dose out and just use Nitro the engine is noisier uses more fuel and has a rougher idle together with black smoke on acceleration.

When i fill up again and use the 2T it is like a different car to drive is so smooth and i would put it up against any petrol engine even when from cold........and is not a placebo effect otherwise i would not bother to use it.
I've been doing a bit of reading (for a change), and cannot see how different diesels can make a difference because of how they burn and don't go bang. That is how scientific I get.
Also, I've never seen any black smoke yet.
 

KeithJG

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@Capra...........do a bit more reading in the correct place!
 

Capra

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@Capra...........do a bit more reading in the correct place!
This was your statement.....
"As said back a bit the ECU will also adjust the ignition according to what fuel is being burnt also if the engine runs smoother then the combustion must be cleaner so therefore must give better performance even if it can`t be measured"

You just made an assumption that there must be more power! Can you find a link that proves expensive diesel will give me more power?

This is info that I have found regarding premium diesels. Seems that performance can be maintained by keeping an engine clean rather than seeing an increase.

"Because diesel engines don't ignite fuel to create power (fuel is added to the air that is compressed instead), premium diesel doesn't usually feature a higher octane rating. Instead, this more expensive super diesel will feature chemicals in its mixture that are designed to shift soot deposits and other oily build-up from within the engine's fuel system"
 
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oigle

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This was your statement.....
"As said back a bit the ECU will also adjust the ignition according to what fuel is being burnt also if the engine runs smoother then the combustion must be cleaner so therefore must give better performance even if it can`t be measured"

You just made an assumption that there must be more power! Can you find a link that proves expensive diesel will give me more power?

This is info that I have found regarding premium diesels. Seems that performance can be maintained by keeping an engine clean rather than seeing an increase.

"Because diesel engines don't ignite fuel to create power (fuel is added to the air that is compressed instead), premium diesel doesn't usually feature a higher octane rating. Instead, this more expensive super diesel will feature chemicals in its mixture that are designed to shift soot deposits and other oily build-up from within the engine's fuel system"

Won't prevent but will reduce. See posts above by Craig and myself.
 

Capra

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Won't prevent but will reduce. See posts above by Craig and myself.
So not only do you fail to get any performance gains, it will only reduce the build ups of soot?
 
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