XSeries-forum

X5 30D e70 61 plate with 19.5k & 14months in, car predominantly always run on supermarket fuel as its closest & cheapest fuel.

Thought it was starting to run a bit rougher on tickover and mpg was down from 34-35 on OBC to 32-33.
NOTE: On my car any brim to brim fillup & mpg calculation is always without fail 2mpg lower than OBC  ???
Also I do realise car take more energy to run in winter more energy=higher fuel usage

Did a few searches on fuel suppliers etc and benefits real or imagined of premium vrs supermarket.

Decided to get millers fuel additive just to use every 3rd fill up or so on supermarket, works out about 2p per litre.

Ordered of ebay so when waiting for delivery I filled up with BP Ultimate & did 461 miles this week on normal usage (for me = relative test against my normal driving).  TBH car sounds and ticks over a bit smoother BUT fuel economy is exactly same NO DIFFERENCE!!

I have filled up again tonight with BP Ultimate & will give it 1 more try.  Not exactly holding my breadth though.

Around here Tesco 138.9lt  BP Ultimate 147.9lt  (that 9p litre more) 70lt to fill = £6.30 more for premium fuel for no benefit except smoother tickover. 
I think the advertising & marketing men are having a chuckle at my expense. >:(

Have now got my miller fuel suppliment & will use it after finish BP Ulitimate test next week.  TBH not expecting increased mpg with millers but by all acounts its does help smoother tickover, and at 2p litre cost is still 7p lt cheaper than BP Ultimate  ---- millers here @ £10 bottle of 500ml on ebay & cheapest I found (halfrauds were £12.50 I think)  http://www.ebay.co.uk/itm/Millers-Diese ... 4910467%26)

OK so its not entirely too scientific, just my experience so far  But early indications look like I'll be returning to supermarket cheapness with every 3rd or 4th fill up supplimented with millers to keep system clean & smooth.

Had a few diesels and usually go for v power. It seems to be less smokey compared to regular shell.

+1 for V Power. I'm a low mileage driver so added cost not an issue, and it seems to be the best fuel for the health / performance of the car.

My OBC readings are almost spot on or ever so slightly reading less than actual, so on the good side.  I was recently in Southern Ireland and filled up.  First time my OBC was showing over.  I put it down to not getting the full litre per litre! 

Do you get the same discrepancy with the readings when using BP?

Don

OBC is aways 2mpg more than actual calculated from fill up to fill up, been like this from new, thought it might get better once car was well run in. 

Will give VPower a go at shell next week, see how that compares.

My E39 used to run much smoother and better on premium diesels. Less smoke smoother idle and better mpg. It's only marginal but at current prices I find their is enough extra range on a tank of premium to cover the price. But no free lunch .

The X5 seems better on ultimate diesel. I assume its like chipping though if you drive the car for fun mpg goes out of the window. If you drive smoothly there is a bit extra to reward you.

I'm getting 36-39 mpg on 40 mile round trips to gloucester and back. Pretty pleased with that.

at what speed do u go on teh motorway? 60? lol

was it 5th gear who did a study on various fuels? from memory only shell vpower that proved to be any different and better... everything else was the same.

Checked it again this week after fill up and mpg is within 0.5mpg (but still below) of the OBD, so that equates to 1.5mpg better for me on second BP Ultimate fill up.  This extra mpg virtually eliminates the extra cost of BP's standard diesel and 2p litre more than supermarkets, and you get smoother running into bargain.

So all in all its prob worth filling up with premium diesel.  No point spending £000's on a car & then to go cheap on a few quid for fuel.  :drive:

Would be like buying a racehorse and feeding it cornflakes.

[quote="jaynana"]
at what speed do u go on teh motorway? 60? lol

was it 5th gear who did a study on various fuels? from memory only shell vpower that proved to be any different and better... everything else was the same.
[/quote]

I have the limit / warning set at 85. I usually stick to the speed limits and/or keep with the flow.  If I want some fun I find a few twisty roads that take handling rather than a bit of extra speed on the motorway.

I wouldn't say I hang around .

I understand that 5th gear used a car with a very limited/restricted engine so it neither generated any extra power or fuel efficency. I've found BP ultimate and V Power both of which are 55 cetane rating do give a small mpg bonus enough to cover the cost. Or a tiny bit better power delivery at least in the 3.0 Diesel engine.  Most diesels vary between 51 and 55 cetane.

The e39 had a few issues probably really lumpy idle and fuel economy was dropping badly. But on premium fuel it still ran smooth and efficiently.

Can't say it will benifit all cars but I would imagine that some cars would do better than others.

I've started logging fuel with road trip app so will see in a few months how different fuels compare on a tank by tank basis. .  Another forum member did that and there was a clear link between the premium fuels and his average mpg.

We're not talking an extra 10mpg. It's marginal but I find the price matches the benifit and the engine runs smoother and most likely cleaner too.

The smoothness is probably due to additives libricating the fuel system. As most diesel is low sulphur now. Which is not ideal for the engine.

Some people suggest running on cheap diesel plus a few hundred ml of two stroke oil added to the tank. But not sure I want to try that in my engine .

A good read..

http://www.honestjohn.co.uk/forum/post/ ... tm?t=89013