Premium Diesel

Strider590

Paradigm wrote: »

That's not strictly true though is it? If IIRC you run a track car with a very high compression ratio... bet you don't put standard 95 octane in that!

Are we going to have to go into THIS yet again?

I have a race tuned high compression engine, it uses higher octane fuel because if it did not, it would suffer pre-ignition and destroy the pistons.

The octane rating itself has nothing at all to do with the power the engine kicks out.

Paradigm

Strider590 wrote: »

Are we going to have to go into THIS yet again?

I have a race tuned high compression engine, it uses higher octane fuel because if it did not, it would suffer pre-ignition and destroy the pistons.

The octane rating itself has nothing at all to do with the power the engine kicks out.

Not on it's own I'll admit but for high performance engines designed for 99/100ron... it's a major reason they produce the power they do.
How much power would you lose if you had to reduce the compression enough to run on 95ron fuel?


To say this "It's got sweet FA to do with power" is totally incorrect...

Iceweasel

Paradigm wrote: »

Not on it's own I'll admit but for high performance engines designed for 99/100ron... it's a major reason they produce the power they do.
How much power would you lose if you had to reduce the compression enough to run on 95ron fuel?


To say this "It's got sweet FA to do with power" is totally incorrect...

Surely the easy thing to do would be to retard the ignition, not alter the compression ratio.

Strider590

Iceweasel wrote: »

Surely the easy thing to do would be to retard the ignition, not alter the compression ratio.

This is what you'd do, but in doing so you'd lose optimal ignition advance, which would in turn reduce your power output. But it's the engine not the fuel that produces power.

People need to get this octane = power concept out of their heads, it's been drummed into us with factually incorrect advertising for decades. But then in many respects, if everyone knew the truth, they'd mostly stop buying it and it'd start disappearing off forecourts

My original point was that BP "ultimate" unleaded has no ethanol content and as such will be give better MPG, therefore it is possible that the "ultimate" diesel does the same (in diesel engines).

Paradigm

Strider590 wrote: »

People need to get this octane = power concept out of their heads, it's been drummed into us with factually incorrect advertising for decades.

So what you are trying to say is that high octane fuel doesn't=more power for the average driver, isn't it? That I'd agree with.

Marktheshark

Basically if you think you need more expensive premium brand diesel.
You might as well have bought a petrol, any saving is out of the window.

Paradigm

Marktheshark wrote: »

Basically if you think you need more expensive premium brand diesel.
You might as well have bought a petrol, any saving is out of the window.

Ah... but then we'd be talking about "premium" vs supermarket petrol.

Marktheshark

Has anybody ever produced a definitive lab test to prove the premium brand gives more MPG.

Zandoni

Extra MPG is great but I'm also interested in the cleaning properties of the diesel.

Weird_Nev

Paradigm wrote: »

Not on it's own I'll admit but for high performance engines designed for 99/100ron... it's a major reason they produce the power they do.
How much power would you lose if you had to reduce the compression enough to run on 95ron fuel?


To say this "It's got sweet FA to do with power" is totally incorrect...

I agree totally. Pretty much every modern ECU has knock sensors and will retard the ignition as soon as they sense knock. And higher RON is more knock resistant.

Grab a decent high revving Petrol engine and try it, you can actually tell the difference. My impreza ran like a dog on 95 to the point you didn't want to rev it out.

RON has a huge amount to do with power, either in a high performance engine or when mapping. There's a reason you use E85 if you want huge power from a tuned turbo.

With regards to the diesel... sorry, it's a diesel. If you're concerned with MPG, drive it frugally. Personally I think that high quality fuels and the additives are worth having, but the premium price of the posh stuff is never offset by increased MPG in my experience.