Normally I fill my 04 tdci Mondeo with Shell diesel because its on my commute and does reasonable mpg, and is actually one of the cheapest around.

Mrs FD borrowed my car the other day and filled up with Saisnburys diesel. The mpg is very slightly lower, but the biggest difference I have noticed is that on acceleration the Sainsburys fuel does not leave a big plume of smoke behind the car, where as if I fill up with Shell it leaves an embarassing smoke screen behind the car !

Why would this happen?

They’ll claim it’s due to detergents and the like, to clean your engine out while you drive.

There is nothing embarrassing about smoke screens! especially when you are on the run from baddies 😀

it’s burning rubber, due to the massive extra power surge

Thats weird, I’ve just had the exact opposite experience! I usually use shell as there’s one just round the corner from me but I got taken in by Sainsburys cheap prices the other week. The smoke was amazing! Zero power and rubbish mpg, you just had to look at the accelerator and the car behind vanished! I used that up and put in some v power and it’s running sweet now, hardly any smoke.

don’t engine management systems ‘learn’ your fuel characteristics and set up for those; when you change fuel it would take a while to learn a new set…?

i’d (probably wrongly due to my lack of mechanical knowledge) assume that its cos you’re wife has ragged it to the limit in each gear before changing up, and cleared a load of soot etc from your pipes, so now when your driving its not pumping out black hell on the odd occasion you put your foot down 🙂

i have to remind myself to drive in higher revs once a month to do this, as i’m such a chilled driver that i never go above 2000revs unless im on a motorway in 5th gear (all the way up to 3000revs! 😯 lol)

Can you actully see the smoke yourself, out of the rear window?? That HAS to be too much – surely there is a problem?

Mind you, whenever I see a smokey diesel car, it always seems to be a Mondeo or maybe a Focus…

Rachel

fuel is done to certain standards and meets quality/octane standards marks all the differences are marketting. They all come from the same refinery /distribution network

My wife drives like a little old lady so when I get in her car and give it a bit of a ragging there’s always plumes of soot pouring out the back of it (Audi Tdi) for the first few miles, seems to sort itself out after a while though.

Could be different additives burning off soot from the exhaust.

Neighbours Moondeo spews out a smokescreen every time it starts up, at the same time sounding like a bag of spanners being shaken.

Might agree with the concept that the car runs cleaner on more basic diesel than the fancy stuff – especially Shell, anyone else old enough to rember that fuel they did (was it Formula Shell???) claiming to enhance everything about the engine, and long terms testing showed it did damage?

Nowt wrong with supermarket fuel, all fuel on sale has to reach a minimum British Standard anyway, it is the branded fuel that supposedly exceeds this standard.

fuel is done to certain standards and meets quality/octane standards marks all the differences are marketting. They all come from the same refinery /distribution network

There are MINIMUM values for certain specs for fuels, but not all of them. In diesel terms, the minimum cetane number is something like 51, but fancy diesel (ie BP Ultimate or Shell Optimax etc) is min 55. It makes a significant difference in starting and smoothness, and also improves power and economy.

In petrol terms I am less sure but I think they have to have a certain oxygen content, and for cheap fuel they add something to meet that spec that can reduce the energy density..? Not sure.

In any case there can be big differences between fuels that meet the legal specs.

I dunno about the OP’s situation – could be a number of factors conincidental or as yet undiscovered. However fancy diesel (Ultimate etc) does not make my car smoke more, but I never see visible smoke anyway. It does make it smoother, more economical and a smidge more torquey tho.

sounding like a bag of spanners being shaken.

I heard an East German tank that had been standing for a few months fire up once (12 litre CZ diesel) it sounded like a skip full of spanners in an earthquake. Seriously bad. 😀