Supermarket or Super Pricey Fuel, does it make a difference on MPG?

terrywindy1

A2OC Donor
So my 1994 Audi 100 2.5 tdi best trip 62.6 mpg to Brighton
FSi from Leeds 59.1
TDi 90 77.3 to Lancaster I did use Pulse and Glide
And 1990 Audi 3.6 V8 Quattro 32.5 mpg to Northampton
Are all reading wrong ?
All of these trips are one way from cold
 

terrywindy1

A2OC Donor
I will check the next tank between trip and fuel receipt to confirm the DIS accuracy, looking at Fuelly I seem in the normal range. Note this is journey specific data and a long one at that so it helps a lot, I don’t hit above 70mpg until Exeter when leaving Cornwall, that shows how much a cold start, slow narrow lanes and lots of hills impacts the mpg.
We are talking about one off trips NOT every day driving my 36 mile round commute in the 90 Tdi I get between 58mpg and 64 mpg but again it's nearly all motorway and no traffic
 

Robthebank

Member
OK, so some good excitement and discussion here!
To clarify my purpose in starting this thread, at present I'm doing around 1000 miles / week, and I was curious to see if the brand or price of fuel has any correlation with economy measured as mpg, any other perceived difference of these types of fuel is difficult to prove via my testing. In regard to producing the brand X versus brand Y data, i thought it would be best to do that by testing the fuels over the same long route, as a tank to tank test would be meaningless if the journeys per tank were different, hence I'm going to do the same route multiple times with different fuels, and as much as I can keep everything else consistent, I expect speed and terrain will have the biggest difference on economy thus I will cruise at the same speed, 65mph on dual carriageway and then within 110% of limit everywhere else, where I have an option, some places I wont have an option, traffic jam / lights / roadworks etc.. hence the journey average speed may change. So two journeys with the same real average speed should give the best comparison.
I'm not trying to show what my cars long term any terrain / journey average is, or what the best I can do is, I could get rid of the mpg numbers altogether if they are controversial and just call for the first run 100% and then the others could be 95 or 102 etc... I have no interest or prestige in telling you an inflated number. Although I will get my fuelly account back up and running again, although If I remember correctly it takes a couple of tanks to get an accurate average figure as the tank full point can make a difference on the calculation (i.e you need to fill to the same point).
 

PlasticMac

Member
Just had a browse on the Shell website, and for both Shell V Power petrol and diesel, they major on the engine cleaning properties, rather than any economy benefits. So, as I've said before, any significant benefits to us, of pricey fuel in in longevity and reliability, not maximising mpg. As others say driving style and type of journey are the primary factors influencing mpg.
Only my opinion of course. Mac.
 
Last edited:

Un4tural

Member
Just had a browse on the Shell website, and for both Shell V Power petrol and diesel, they major on the engine cleaning properties, rather than any economy benefits. So, as I've said before, any significant benefits to us, of pricey fuel in in longevity and reliability, not maximising mpg. As others say driving style and type of journey are the primary factors influencing mpg.
Only my opinion of course. Mac.
My TDI 90 is struggling on MPG and i can see many members getting higher numbers than me (I'm around 40-50mpg quite heavily depending on how i drive with this car) will go have checks once i have it back on four wheels to pump the numbers up. (the 17" sport rims) (same 300mile intervals to fill up end up filling about 24-31liters which is a lot wider variation too)

My previous TDI 75 (early 2001 model) would get 65-70 no matter how badly i abused it, spent good few refills driving purely with my foot welded to the floor and still measuring at the pump it'd be no less than 60mpg - that is mostly city driving too. No idea how - would fill it up every 300miles and i'd have 20-24 liters at the pump, 24 being in winter when webasto was doing it's thing. Loved the silly economy. (standard SE rims, 16" i think).
 
Could someone advise on the safety aspect of coasting - and anyway as I understand it you wouldn't be saving fuel.
On fuel consumption, I've seen better than 70mpg on a few occasions, 73.1mpg is my best. My A2 is the TDi75, a well-known remap and 6 speed box, but I've not found any difference between Shell and Tesco fuel. Using a 200:1 mix with 2 stroke oil seems to make it run more smoothly but it's got to be the right specification. Also, it seems to be slightly worse with the 17" wheel option, and best with the 15" pepperpots.
 
Last edited by a moderator:

depronman

A2OC Donor
Could someone advise on the safety aspect of coasting - and anyway as I understand it you wouldn't be saving fuel.
On fuel consumption, I've seen better than 70mpg on a few occasions, 73.1mpg is my best. My A2 is the TDi75, a well-known remap and 6 speed box, but I've not found any difference between Shell and Tesco fuel. Using a 200:1 mix with 2 stroke oil seems to make it run more smoothly but it's got to be the right specification. Also, it seems to be slightly worse with the 17" wheel option, and best with the 15" pepperpots.
Trev,
That would be expected on the wheel front, the 17" sports wheels are heavy and therefore increase fuel consumption, as does the extra width of rubber on the road, hence the best for economy is a light weight 'push bike' width tyre, but this is worst for grip, so there is a sweet spot where grip is adequate and economy is not adversely affected, this is pepper pots and suitable narrow tyres on the A2
 

Robin_Cox

Member
Best mileage I've had on a long run was when I picked the BHC car up near Wembley ; filled up with Shell's premium diesel and then was stuck in the usual traffic on M1 and M6 coming north, only speeding up significantly north of Lancaster. Fuel light came on at 450 miles a couple of days commuting after arriving home, but then the 42 litre tank only took 35 litres, suggesting I would have gone well north of 500 miles - and that was with both dud thermostat and an erratic coolant sensor (gauge-feed rather than engine judging by ODB reader). I've hypermiled (for me) to Aberdeen and back getting 68mpg, and done many trips Dundee to Plymouth averaging mid to high 50s mpg but averaging around 68 mph including stops - this is all on supermarket fuel though.

I'm getting ready to refurb petrol injectors on the AUA - apologies for thread swerve, but apart from fuel, any thoughts on getting a set of BHC injectors refurbed and likely effect that this could have on fuel-efficiency?
 

DJ 190

A2OC Donor
and anyway as I understand it you wouldn't be saving fuel.
Well, you've really got that wrong! It makes a BIG improvement in m.p.g.! How do I know that? My A2 has the sophisticated colour DIS fitted by Tom (Timmus) One of the features is average M.P.G. So if I go into neutral, up, up, up goes my M.P.G.! It's immediate! There's no better illustration than looking at that display! I'm not sure what your concerns are regarding safety? You still have the brakes and steering. I may be wrong, but I think that some modern cars have this feature as an aid to economy? (Or maybe I'm thinking that one of the cylinders goes onto standby?) I DO know that the action of "coasting" goes back a long, long way! Oh, I use the same 200:1 2-stroke addition to the fuel. It is noticeably quieter. I'm ready to fit the 15" pepperpots, too.

David
 

Robthebank

Member
Re coasting, it’s a bit of an urban myth that it’s illegal in the UK, it’s not as there is no specific law against it but if you were involved in an accident it could be argued that you weren’t in direct control of the vehicle. And it’s correct that most modern autos that have an economy driving mode will auto “glide” when off throttle to save fuel, but they will also reengage a gear if the car speeds up (going down a hill).
 

Proghound

Admin Team
Could someone advise on the safety aspect of coasting - and anyway as I understand it you wouldn't be saving fuel.
On fuel consumption, I've seen better than 70mpg on a few occasions, 73.1mpg is my best. My A2 is the TDi75, a well-known remap and 6 speed box, but I've not found any difference between Shell and Tesco fuel. Using a 200:1 mix with 2 stroke oil seems to make it run more smoothly but it's got to be the right specification. Also, it seems to be slightly worse with the 17" wheel option, and best with the 15" pepperpots.
Trevor, it's my understanding that a trailing throttle is the safer way to save fuel rather than coasting in neutral or with the clutch out, because you still get engine braking. Also, while you're off throttle it is actually using less fuel than at idle, as it all-but chokes off the entire supply. I have actually seen this reflected in the instantaneous readings (in another car, not my A2). However the engine braking means that you can't spend so long off-throttle before having to maintain speed or negotiate the next hazard. Depending on the relative consumption rates of idle and trailing zero throttle, this may mean that you don't save as much fuel.
 
Well, you've really got that wrong! It makes a BIG improvement in m.p.g.! How do I know that? My A2 has the sophisticated colour DIS fitted by Tom (Timmus) One of the features is average M.P.G. So if I go into neutral, up, up, up goes my M.P.G.! It's immediate! There's no better illustration than looking at that display! I'm not sure what your concerns are regarding safety? You still have the brakes and steering. I may be wrong, but I think that some modern cars have this feature as an aid to economy? (Or maybe I'm thinking that one of the cylinders goes onto standby?) I DO know that the action of "coasting" goes back a long, long way! Oh, I use the same 200:1 2-stroke addition to the fuel. It is noticeably quieter. I'm ready to fit the 15" pepperpots, too.

David
I'm just about to start the Institute of Advanced Motorists course so I'll let you know about coasting.
 

Un4tural

Member
I'm just about to start the Institute of Advanced Motorists course so I'll let you know about coasting.
Just curious does this actually make a difference to insurance or is it just a tick box that doesn't really go into any of the calculations with them? if it knocks down 50£ or so a year off insurance it might be worth sitting through? Anyone done it already and have noticed a difference? Sorry bit off topic.
 

damadgeruk

A2OC Donor
Well, you've really got that wrong! It makes a BIG improvement in m.p.g.! How do I know that? My A2 has the sophisticated colour DIS fitted by Tom (Timmus) One of the features is average M.P.G. So if I go into neutral, up, up, up goes my M.P.G.! It's immediate! There's no better illustration than looking at that display! I'm not sure what your concerns are regarding safety? You still have the brakes and steering. I may be wrong, but I think that some modern cars have this feature as an aid to economy? (Or maybe I'm thinking that one of the cylinders goes onto standby?) I DO know that the action of "coasting" goes back a long, long way! Oh, I use the same 200:1 2-stroke addition to the fuel. It is noticeably quieter. I'm ready to fit the 15" pepperpots, too.

David
Coasting or freewheeling in neutral does not save fuel despite what DIS (colour or std) is saying. Certainly not in an A2.
Many sites debunking this legend, here's one.
 

DJ 190

A2OC Donor
Interesting! It does mention modern cars .... how "modern" are A2's? I wonder why you think that the DIS is unreliable and giving erroneous information? I've mentioned that when coasting, the average M.P.G. figure starts to climb and is an encouragement to use this as a way of reducing fuel consumption. Logically, too, I would have assumed that it was beneficial? I certainly don't look for every occasion to be doing this ..... there are just certain road sections that I use fairly often and that are suitable. I have a scientific approach to things and weigh-up all the available information. That applies to your input, too, so thanks! So I'll avoid making sweeping statements like "certainly not in an A2" Can we be certain of that?

David
 

Un4tural

Member
Interesting! It does mention modern cars .... how "modern" are A2's? I wonder why you think that the DIS is unreliable and giving erroneous information? I've mentioned that when coasting, the average M.P.G. figure starts to climb and is an encouragement to use this as a way of reducing fuel consumption. Logically, too, I would have assumed that it was beneficial? I certainly don't look for every occasion to be doing this ..... there are just certain road sections that I use fairly often and that are suitable. I have a scientific approach to things and weigh-up all the available information. That applies to your input, too, so thanks! So I'll avoid making sweeping statements like "certainly not in an A2" Can we be certain of that?

David
I do think it will depend on which engine A2 as well - per my previous post my old 2001 would get that MPG mostly no matter what, i'd tried to coast as much as possible and only stay in gear doing it "properly" (least from what i was taught not a whole lot i actually applied) and fuel consumption wouldn't be noticeable different.

With current TDI 90 coasting makes it worse - would coast anyway mostly cause DMF felt like it was going which has indeed gone. I've not taken scientific measures but few fill ups i tried to coast as much as possible i'd end up with less (speed up coast in neutral speed up again, coast down hill etc.)

However I would wager this would vary between TDI 90 as well as mine is definitely on the lower end for MPG numbers. DIS does indicate nice numbers when coasting but it is not indicative from what I have seen - when i'd coast more average MPG would be indicated a few higher than when i did not however at the pump when normally DIS is quite accurate to probably about 4mpg, when i'd coast more it would appear more "optimistic" with the numbers.

That's my 2 cents from experience I've had though.
 

damadgeruk

A2OC Donor
Interesting! It does mention modern cars .... how "modern" are A2's? I wonder why you think that the DIS is unreliable and giving erroneous information? I've mentioned that when coasting, the average M.P.G. figure starts to climb and is an encouragement to use this as a way of reducing fuel consumption. Logically, too, I would have assumed that it was beneficial? I certainly don't look for every occasion to be doing this ..... there are just certain road sections that I use fairly often and that are suitable. I have a scientific approach to things and weigh-up all the available information. That applies to your input, too, so thanks! So I'll avoid making sweeping statements like "certainly not in an A2" Can we be certain of that?

David
A2 is modern enough that the fuel supply will be cut when in gear with no throttle. I'd wager most cars without a carburettor will be similar hence my 'certainly not in an A2' though I'm learning daily too.
I'm not certain why DIS is 'confused', I suspect it is because it is designed to be indicative rather than entirely accurate that it makes assumptions rather than Audi fitting more or more expensive sensors which are largely unnecessary.
It's only relatively recently I discovered my 20+ years of 'knowing' that better tyres go on the front was debunked. All manufacturers I've checked say better tyres to the rear though I still find tyre fitters are unaware of this.
 
Last edited:
Top