XUD9 vs DW8 discussion

[CitroJim]

I always pride myself on understanding diesel combustion fairly well and never understood how cetane improvers can make a significant difference to running at normal running temperatures...

My understanding has always been that the cetane rating of diesel fuel is essentially the opposite to that of octane rating for petrol in that it is a measure of a fuels' readiness to detonate at a given temperature and pressure. It is generally upped to a higher level in the winter to assist in cold staring and this generally is where I've understood a high cetane rating is beneficial - it improves cold starting.

Cetane ratings also influence the ignition delay... i.e. the delay from start of injection to actual detonation. This is longer in the cold than in the warm and is the reason why old-school diesels have cold ignition advance set on their pumps.

On a modern electronic diesel any changes in cetane should be compensated for automatically so no difference in performance should be seen.

Also, a diesel will burn any old hydrocarbon that can be ignited under heat and pressure so once hot what fuel it is any what cetane rating it has should in theory at least, be irrelevant.

Hence why a diesel can run on anything from coal dust to peanut butter. If the pump can pump it and inject it the engine will run and most see no significant performance difference between running DERV or cooking oil in an XUD...

Having said all that I know that many report the 'premium' diesels do indeed give benefits. I'm not disputing it but I've never seen any difference myself in XUDs or early HDis and I wonder how much is down to placebo effect and the fact these fuels may have good detergents in them and any performance improvement comes about from having a clean fuel system as a result of their use...

Your educated thoughts on this would be appreciated as I want to understand it properly... I have not yet seen a satisfactory answer to dispel my belief that it's mostly marketing hype.

[Harlequin]

http://sevron.co.uk/msds/advanced-formu ... -download/

[white exec]

On both BX, XM and D4D, we've often had to put up with less than wonderful performance (i.e. lack of torque) after having to fill up in desperation with budget or supermarket fuel. All I can say is the difference in driveability can be marked.

I don't bother with posh diesel (super super premium advanced, or whatever, and higher priced), but just buy standard grade - usually Repsol, which is consistently good. Many friends here have found the same, with older and new cars running on an exclusive diet of supermarket/budget fuel encountering problems. Diesel workshops here advise against doing this, and suggest a combination of good-quality fuel and an Italian tune-up to get things working properly again.

I think it depends on the journey, and what terrain you encounter. Here in the mountains, being able to tackle steep corners and inclines is of daily importance, especially heavily loaded.

It really isn't just marketing hype. I agree with you, Jim, diesels will run on almost anything, it's just a matter of how well they run though.

[van ordinaire]

As some of you will know, my sudden interest in additives arose because of a particular issue, but, having caught up, a few random though, hopefully, relevant thoughts:

My old van does seem to run better when there's veggy (usually sunflower oil) in there, even if it's only 5 litres to a tank: placebo or lubricity?

What's the difference between a diesel & a multifuel engine (apart from the fact the latter will run on petrol)?

DERV - now there's a dear old fashioned term; how/why isn't it diesel?

What exactly was "bunkering service" - & why don't we need it any more?

Is it really being suggested that we use a supermarket's own brand additive to cure the deficiencies of their fuel? The irony is delicious (& probably smells better than the additive).

Do I correctly understand that one particular Wynn's product was chosen over the other two for its smell - or was it simply because that was the only one that was available locally?

Why is (a lot of) Eurodiesel blue?

[white exec]

The three I mentioned (Wynns, Millers and 3CV) all look and smell the same, and have almost identical MSDS sheet ingredients. The choice was down to local availability - currently 3CV.

[elma]

I always found xuds smoothest on BP or shell diesel, best economy too. I saw no improvement from super diesel either, but wouldn't expect to.
My v6 is similar but happily drinks at Texaco as well, high octane only. Filled with regular unleaded it loses torque and smoothness. Fill with Esso, supermarket or other budget fuel and it barely runs or sometimes refuses altogether (asda fuel caused that and I thought I'd broke it)

[myglaren]

Mine seems better on Torq standard diesel than anything else, including 'super-premium' diesel including Torq's own.
Been adding Redex for six months now and no difference whatsoever.

It did do very well on Bio though, n longer available.

[CitroJim]

None of my cars seem to care a jot what fuel they have...

My Activa might be a tad more frugal on premium but that's all and fully expected given it's injection is adaptive to different octane ratings... To me the difference is hardly noticeable...

The Pug of Love and Gabriel are not fussy at all..

Must be how I drive...

Now, my bike engine is totally different and that has very critical and specific fuelling requirements

[Hell Razor5543]

Burger and Chips?

[CitroJim]

Burger and Chips?

No!!!! That’s akin to putting used veg oil straight into an HDi

[Hell Razor5543]

Ah, but the bun was some of your own home baked bread! Surely that makes a difference?

[CitroJim]

Ah, but the bun was some of your own home baked bread! Surely that makes a difference?

Yes, a big difference I'm a vegetarian so as long as the burger is either bean or fish

I don't eat processed meat of any sort...

[ekjdm14]

DERV - now there's a dear old fashioned term; how/why isn't it diesel?

DERV is simply an acronym for Diesel Engined Road Vehicle as I understand it...

[elma]

That's right but many will say it's diesel oil for road vehicles. The e clearly standing for oil for. Apparently it's a ww2 army acronym and they meant diesel engined...

[van ordinaire]

. . . Apparently it's a ww2 army acronym and they meant diesel engined...

A lot of miitary slang found its way into common use, prang, gremlin &, of course, jeep being more obvious examples BUT how/why did "DERV" come to appear on the globes on forecourt pumps - & what did it replace?

Oh, & why did the army have an acronym for something they didn't have for another 50 years?