Just an observation on supermarket fuel

MrSix said:
Not when they drive a diesel ;)
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Oh they do. Especially when they don't get the fabled 60mpg everywhere, the DMF blows up, the DPF clogs and it suddenly dawns on them that they put up with the tedious thrum and didnt end up saving much money.

I guess thats when it changes from being about mpg to being all about the torque..

... at the flywheel.
 
Uriel said:
I've not seen any difference in calculated mpg between supermarket and branded fuel that couldn't be put down to driving style or the weather. It's just the discrepancy between trip computer and calculated.
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That just makes your claim even more ridiculous suggesting that the trip computer knows when you fill at tesco rather than shell even though in the real world its identical fuel returning identical real world mileage.
 
How do the trip computers work??

Obviously the ECU knows exactly how much fuel is being squirted in everytime an injector opens. But do they use that data for the computer
 
I would guess the trip computer estimates the rough volume of fuel injected. If that fuel has higher calorific value (as you would get for a higher proportion of petrol relative to ethanol) it will increase the amount of energy created when the same volume of fuel is detonated. Hence slightly more torque, resulting in lower throttle required for the same performance. Ergo more work done per detonation and higher mpg. The computer only knows the volume hence different accuracy for different fuel. If the computer could tell the calorific value and compensate for it there wouldn't be a discrepancy.

As for octane, the car is supposed to run on 95 RON. I doubt its capable of advancing the timing enough to take advantage of higher octane fuel.

Detergents might increase efficiency by cleaning out some crap but I wouldn't expect dramatic improvement.

I've read on Honest John and RAC sites that everyone starts off with the same base fuel, collected from the depot. The additive package (including ethanol, detergents etc) is then added according to the retailers specification. Supposedly the tanker drivers have different additive identification cards or something for different retailers.

Shell and Esso have both claimed that their respective additive packages for their 95 RON fuel can increase fuel efficiency although the ASA forced Shell to tone down their claims for 'exaggerating' the benefits. That's not that there were no benefits - just exaggerating them. With Shell Fuelsave the ASA did not dispute the clim of greater mpg. It was just that they didn't think the data set was large enough... http://cars.uk.msn.com/news/shell-fuelsave-ads-banned
 
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I used to work for TDG, on the contract supplying fuel on behalf of Tesco. Our driver's would go to whatever their local refinery was, i.e. Stanlow, Immingham, Lindsey, Grangemouth, Seal Sands etc, queue up with the tankers that belonged to the refinery operator (Shell, Esso or whatever) and load fuel from the same tanks as them. Tesco at least, weren't buying a different grade or product, but looking across the country as a whole, the supplier will differ.

For example: Tesco garages throughout the north west would be supplied by Shell from Stanlow, while in the east midlands they'd be supplied from the Lindsey refinery, which is operated by Total.
 
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MrLOL said:
Co-incidental

there have been numerous tests done and the variation between one unleaded 95 and another is negligible

The other problem you've got is that your supermarket forecourt doesn't always get its petrol from the same supplier. Its not uncommon for the supermarkets to use more than one supplier to meet demand.

And then of course theres the whole issue of the fact that supermarkets don't actually make petrol. So chances are, you could be buying the same fuel thats in the esso garage down the road.
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The fuel is mostly the same until the tanker picks it up and adds the additive treat as determined by the customer. Supermarkets are likely to go for the cheapest option...

That's about all I can say on it, but they certainly don't have tanks Customer specific fuel sat at fuel depots.

Most supermarkets also have contracts with a supplier to be the only supplier of a product, fuel being no different.
 
Simon said:
The fuel is mostly the same until the tanker picks it up and adds the additive treat as determined by the customer. Supermarkets are likely to go for the cheapest option...

That's about all I can say on it, but they certainly don't have tanks Customer specific fuel sat at fuel depots.

Most supermarkets also have contracts with a supplier to be the only supplier of a product, fuel being no different.
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The way some people talk you would think the depots have a Tescos / Asda / Shell / BP / Morrisons / Esso / Texaco loading bay........
 
Don't know about this country but this is how it works in the US... http://www.toptiergas.com/

All commercial fuel in the US should meet the EPA minimum standard but several auto manufacturers recommended that the minimum detergetn specification is suboptimal. They created their own 'Top Tier' minimum standard that retailers could sign up to. May not be as relevant here as I don't think our minimum standard is as low as the EPA (certainly isn't on octane).
 
[TW]Fox;20962810 said:
Oh they do. Especially when they don't get the fabled 60mpg everywhere, the DMF blows up, the DPF clogs and it suddenly dawns on them that they put up with the tedious thrum and didnt end up saving much money.

I guess thats when it changes from being about mpg to being all about the torque..

... at the flywheel.
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Most modern petrols have DMFs now, and all manufacturer torque specs are measured at the flywheel which means diesels still have way way more than their petrol counterparts :p

Oh, and 700 miles between fill ups :)
 
you-sir-name said:
believe me when in say near enough every possible supermarket and major fuel company will at some point during the week load fuel for delivery to their own branded forecourt from our depot.
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I live more or less next door to a storage yard in the North East he's not wrong :)
 
Well - possible humble pie and few of you will be surprised. Just filled up at Esso and it looks like the last BP tank was actually 4mpg (calculated) under the trip computer reading. Still - slightly different pump design and I suspect that I may have squeezed in an extra litre or so.

Having said that, BP and Esso are the same price as the supermarkets round here at £130.9. Total has gone up to £134.9 so avoiding there.
 
Lucero said:
Most modern petrols have DMFs now,
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But they don't fail anything like as much because of the lower torque at the fly.

and all manufacturer torque specs are measured at the flywheel which means diesels still have way way more than their petrol counterparts :p
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lol

Consider the relationship between torque and revs, then come back and tell us if you've worked out why 400nm in a diesel doesn't deliver the performance of, say, 330nm in a higher revving petrol engine.
 
[TW]Fox;21112294 said:
Consider the relationship between torque and revs, then come back and tell us if you've worked out why 400nm in a diesel doesn't deliver the performance of, say, 330nm in a higher revving petrol engine.
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Living in a hilly area, I did like being able to cruise up steep hills in 4th on a 110BHP engine.

But yeah, assuming you're in an automatic, can be bothered to change down occasionally, or have a much more powerful engine in the first place it makes little difference.

Edit: Oh yeah - petrol goes to 11 BTW...
 
Going back the sort-of-original topic, even in my 12 year old Fiesta I see on average 1-2mpg higher using Shell fuel than I do supermarket. The car even feels noticeably nicer (not so much smoother, but just a little bit nicer, I can't put my finger on it).
 
[TW]Fox;20962810 said:
Oh they do. Especially when they don't get the fabled 60mpg everywhere, the DMF blows up, the DPF clogs and it suddenly dawns on them that they put up with the tedious thrum and didnt end up saving much money.

I guess thats when it changes from being about mpg to being all about the torque..

... at the flywheel.
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Yes, because that happens to every diesel, everywhere, every 5 minutes.

Where as a petrol car never breaks down.

Ever.

;)

You've only got to look at the first page of the forum as of now to see FOUR petrol related car problems, and.........................no diesel ones.
 
atpbx said:
Yes, because that happens to every diesel, everywhere, every 5 minutes.

Where as a petrol car never breaks down.

Ever.

;)

You've only got to look at the first page of the forum as of now to see FOUR petrol related car problems, and.........................no diesel ones.
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I see a water pump, alternater and power steering pump failure on the first page, last time I checked a diesel had all these too?

All cars have issues but if a turbo or high pressure injection or particulate filters are not fitted them obviously they won't break...

As soon as you start fitting this stuff to petrol engines you get the same problems. Hello BMW N53 for example.
 
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