Diesel just isn't diesel.

[Doggy]

FWIW guys, all 3 of my HDi's have fired up after what seems to me to be the same amount of cranking, hot, warm, cold or in the occasional -6 degrees or lower temps we sometimes get here. At the very bottom end of this range, the glowplug light will stay on for a few seconds, but all mine have started every time without waiting.

When it's really cold, (by UK standards), HDi's do clatter a bit more initially. I believe this happens until the combined effects of the fuel line heater and glowplugs enable the pre-injection charge to actaully detonate, (which it can't quite manage when really cold).

[gumby6371]

I put a dose of Forte in every other fill up as a cleaner and nothing more (get it free from a friendly storeman at work so why not).
As a former XUD owner I can honestly say that running a 50/50 mix of tesco diesel and veg oil I lost between 1-2 miles per gallon. 37-38 on pure diesel around town and 35-36 on mixed stuff.
That was pretty consistant over a 2 year period therefore the difference between premium diesel and supermarket stuff would have to be similar to diesel and veg oil to make it viable????
My old LX had no electronic jiggery pokery for fuel usage so I always put 10 gallons in when the light came on and monitored the miles covered, always came back on at 370 + or - 10 unless I did some long journeys to the coast and stuff.
I know a few people who regularly run the red stuff in there cars and the only difference they find is a bit more engine clatter when the engine is cold.

My personal opinion is premium stuff is probably a bit smoother and quieter but the increased miles per £ is negligable and thats the important bit to me.

The only 100% answer would be run the same car round a test track and see which travelled further but as I said before a 5% increase in miles covered with a 5% increase in cost is no gain to me.

I have a similar opinion on the 'buy a petrol if you only do short journeys' argument, I do mainly town driving but give me a car that is affordable to own and can average 35MPG+ around town with the same room my 406 has and I'll change my opinion.
The 2.2 with a binding brake and the turbo wastegate stuck closed was doing 32 to the gallon which is the same as I got from my 1.0 punto!.

Thankyou and goodnight

[KozmoNaut]

When it's really cold, (by UK standards), HDi's do clatter a bit more initially. I believe this happens until the combined effects of the fuel line heater and glowplugs enable the pre-injection charge to actaully detonate, (which it can't quite manage when really cold).

Diesel won't detonate even if you heat it to the boiling point, it simply isn't volatile enough. To get diesel to detonate and not just burn, you would have to build a fertilizer bomb like Timothy McVeigh did in Oklahoma back in 1995. I would assume that you're not building bombs out in your shed ;-)

The diesel combustion process is noisy in itself, due to the pressure wave created when the fuel is injected and ignited immediately. Staggered injection pulses mitigate this somewhat, but it's still rather noisy compared to a petrol engine.

The clattering you're hearing is mostly likely due to valvetrain noise. Modern hydraulic lifters clatter a bit when the oil is cold and syrupy. As soon as everything warms up nicely, the clattering should stop.

On older cars with solid lifters and on air/oil cooled motorcycles in particular, valve noise is good, "slappy valves are happy valves". If the valvetrain on an air/oil-cooled engine is silent, something is definitely wrong!

[Bailes1992]

It's normal for a diesel to take a few cranks longer for the cylinder temps to get up to temperature before the diesel will combust.

I've tuned a few fully mechanical diesels... I know the difference between diesel clatter and valve train noise. Diesel combustion is noisy, valve train isn't. Unless it's faulty.

[dirtydirtydiesel]

I have read it & heard it said no end that Bio diesel makes the engines much smoother & less clatterey .
Go on you tube & look up fifth gear high octane fuel tests & also fuel additives tests, tells you all you need to know really you can't argue with the results .
Theres also one where they run some redex in a old corrado V6 those test results are interresting.

[mjb]

Go on you tube & look up fifth gear high octane fuel tests & also fuel additives tests, tells you all you need to know really you can't argue with the results .
Theres also one where they run some redex in a old corrado V6 those test results are interresting.

Just watched the Redex one. I can't believe using it as directed works as well as that - I've always gone for around 10-50x stronger concentration into the last few litres in a tank.

But where's your proof it works? (Apart from the 32 dyno runs and vague talk about flat spots disappearing as reported by a BTCC champion/veteran who obviously doesn't know what he's on about)

[Welly]

as reported by a BTCC champion/veteran who obviously doesn't know what he's on about

Ah but what if he was paid to say all that sh*t? didn't think of that did you?

Theory disproved.

The end.

[mjb]

as reported by a BTCC champion/veteran who obviously doesn't know what he's on about

Ah but what if he was paid to say all that sh*t? didn't think of that did you?

Theory disproved.

The end.

Urgh you're right. I forgot about the 'sponsored product "review"' switch they have on the back of those dynos...

[KozmoNaut]

You're being daft now.

In this Fifth Gear test http://www.youtube.com/watch?v=WTaBngvsPrc, they're using a VW Golf GTI, which of course has a turbocharged engine, and performance pretensions. It also has an ECU capable of advancing timing etc. in the face of higher-octane petrol, so of course there was a difference to record. They don't mention whether they reset the ECU between each run, which could affect how quickly the engine adapts to different fuels. However, an increase of just 5.1hp from ASDA 95 to Shell V-Power? That's worthless.

Vicki Butler-Whatshername claims that she feels "an increase in grunt" a little less than a second after booting the pedal. I think it is quite obvious that the turbo is responsible for that. Plus, a sighted test? Definitely not very reliable.

And on an everyday naturally-aspirated car? There will be no difference or maybe 0.1hp or something completely irrelevant. This can also be seen in this earlier Fifth Gear test: http://www.youtube.com/watch?v=gQghB4asSnI. The naturally-aspirated car (the Clio), gained nothing using the higher-octane petrols. It also backs up the other Fifth Gear video, in that the turbocharged Golf GTI only gained around 5hp from using higher-octane petrol. The Subaru Impreza WRX STI is of course a high-performance rally-bred fire-breathing beast, which is specifically tuned for higher-octane (I believe 100 RON is available in Japan).

But our trusty Peugeots and Fords and Volvos and whatnot are not the same as that Subaru, far from it. In our cars, high-octane petrol means nothing.

As for cleaning properties? Petrol is one of the more powerful solvents available to the general public, it's a pretty damn good cleaner in itself, before you start adding additives.

And as for the diesel test linked earlier, it bears out roughly the same results with a very modest 6hp increase. Will you be able to feel that? Only if you know what's in the tank.

[Bailes1992]

And of course the link I posted where fuels were tested on a rolling road and shown to give an increase in power mean nothing too!

[KozmoNaut]

Which one? The one with the M3 and the MR2? Already covered that one (extremely modest increase on the MR2, within the margin of error).

[Bailes1992]

Which one? The one with the M3 and the MR2? Already covered that one (extremely modest increase on the MR2, within the margin of error).

Umm no... the one with the Citron C5 that they filled up with supermarket diesel and it made 155bhp and then they flushed the system and both premium fuels made 161bhp. But like you say, they are all the same product from the same place.

Funny how I filled my car back up with Shell V-Power and my fuel economy has started rising? But it's the same stuff.

[KozmoNaut]

I covered that in my post:

"And as for the diesel test linked earlier, it bears out roughly the same results with a very modest 6hp increase. Will you be able to feel that? Only if you know what's in the tank."

Like I wrote earlier, turbocharged cars will see a small boost in power, this goes for both petrols and diesel. But does it matter? No. Do you feel the extra power if you don't know what's in the tank? No.

Who even cares about 6hp on a 150+hp diesel? It simply isn't worth the added cost.