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

DJ 190

A2OC Donor
It's usual to have SOME throttle most of the time .... if even to maintain your place in a line of vehicles. It is surprising how, when going into neutral, I find myself gaining on the vehicle in front! I feel that the very best conditions for fuel saving must be with the vehicle in neutral. There used to be a member (MikeMarsUK?) who was an expert at this! He was always claiming VERY high M.P.G. figures. What's happened to him?

David
 

Robthebank

Member
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.
Slightly off topic, but I only spotted that this year after 20+ years as well, statistics show your more likely to have a tyre limited accident caused by over steer, hence rear is more important. So you just need to work out if statistically your an average driver? I spend most of my time travelling in a relatively straight line in all weather on the motorway, so for me braking distance and aqua planning is probably still more important.
 

andrewparkeruk

A2OC Donor
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.
I did the IAM course in about 1993. I found then that only expensive insurers offered discounts. I didn't keep IAM going and the insurance market is very different now.
The course was very well worth doing and I would recommend it.
 

andrewparkeruk

A2OC Donor
Slightly off topic, but I only spotted that this year after 20+ years as well, statistics show your more likely to have a tyre limited accident caused by over steer, hence rear is more important. So you just need to work out if statistically your an average driver? I spend most of my time travelling in a relatively straight line in all weather on the motorway, so for me braking distance and aqua planning is probably still more important.
... so long as you aquaplane in a straight line :)
 

steve_c

A2OC Donor
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.
Tyres first. The very first time I bought a new pair of tyres (almost certainly in 1963) I remember seeing, on the wall in the waiting area, a Pirelli poster advising always fitting new tyres to the rear and explaining the thinking behind it. Of course I had asked for them to be fitted at the front! Nevertheless, it gave me food for thought and I subsequently swapped the wheels over, and have always done it that way since. 25 years later, I saw the exact same poster in a Norwich tyre dealers which made me feel quite nostalgic...
Freewheeling. My lifelong motoring enthusiasm has been the Saab Sport (aka the Monte Carlo, generally identified as a Saab 96). The ultimate 2-stroke engine for performance, if not fuel consumption, I had a small collection, including one 1966 model I purchased new. Being a 2-stroke, it was of course fitted with a freewheel, although the Sport variant's lubrication system meant that the freewheel could be safely left disengaged. For the first 30 years or so, I would always use the freewheel, until changing traffic conditions obliged me to switch it out. Not using the freewheel made very little difference to the fuel consumption, but a lot of difference to the wear rate of the front pads and discs.
The standard DIS on my A2 stops estimating MPG when I take my foot off the throttle, pretty much confirming that in that situation it uses no fuel at all.
 

Robthebank

Member
Re freewheeling, my 10cents, I think you are all correct, but need to highlight the difference between fuel consumption and economy. When you take your foot off the throttle the engine will be supplied with less fuel then if you were idling in neutral. But taking your foot off instigates engine braking and you slow down, going into neutral may even allow you to speed up depending on the terrain hence it can have an economy benefit. Hence a very modern auto box will go into neutral “glide mode” when off throttle to increase mpg, the DSG in a Golf is great at that.
 
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The car's computer cuts off supplying fuel to the engine when there's no load on it - but just on tickover it will be.
A quick Google search shows clearly that coasting is not a recommended technique for reasons of car control and hence safety.
 

depronman

A2OC Donor
I can confirm that all A2’s stop injecting fuel when on over run ie engine breaking
I fully agree though that coasting will use less fuel than having the engine at tick over as engine breaking will quickly slow you down especially on the tdi’s less so on the petrols
Cheers. Paul


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DJ 190

A2OC Donor
There used to be a member (MikeMarsUK?) who was an expert at this! He was always claiming VERY high M.P.G. figures. What's happened to him?
David
Yes, last seen 17th of February 2017 ! So, does anyone know what DID happen to him?

David
 

Dave Kelas

Member
My 2nd last fill up from the yellow light in my 1.6 fsi was 95ron BP unleaded and I averaged 44.6mpg and got 333 miles until the yellow light came on. Last fill I used 97ron BP and after 256 miles I’m holding steady at 46.2mpg, dame driving conditions and same route. It’ll be interesting to see how many miles I get from this tankful
 

Robthebank

Member
So 1st post up-dated with last weeks home trip:
Trip 1 Cornwall - NE, BP Ultimate 75.5mpg Average | 58mph Average (65mph cruising) | 7am Start, traffic clear 15-22degc No A/C, little rain.
Trip 2 NE - Cornwall, Sainsburys 70.6mpg Average | 48mph Average (65mph cruising) | 11am Start, heavy traffic, 15-22degc No A/C, heavy rain.
Trip 3 Cornwall - NE, Tesco 75.0mpg Average | 58mph Average (65mph cruising) | 7am Start, traffic clear 15-22degc No A/C, little rain.
Trip 4 NE - Cornwall, Esso Premium 73.7mpg, Average | 48mph Average (65mph cruising) | 11am Start, heavy traffic, 15-25degc 2hrs A/C nice weather.

So Trips 1 and 3 were very similar, speed weather and gave very similar MPG 75 and 75.5mpg.
Trips 2 and 4 were also very similar, got stuck in traffic just as much as the previous week, and the couple of hours of heavy rain were swapped for a couple of hours of bright sunshine and the AC turned on (now that it works :cool: ) but different mpg 70.6 V 73.6mpg.
So either the rain has a bigger impact then the AC or the Esso premium is better then the Sainsburys budget?
I am starting to think that premium is worth 2-3mpg more then supermarket with the exception of Tesco that performs like a premium fuel.
Early days though, I'm back up and down next week so will do another comparison, maybe Asda Budget and Shell Premium.
 

Robthebank

Member
My 2nd last fill up from the yellow light in my 1.6 fsi was 95ron BP unleaded and I averaged 44.6mpg and got 333 miles until the yellow light came on. Last fill I used 97ron BP and after 256 miles I’m holding steady at 46.2mpg, dame driving conditions and same route. It’ll be interesting to see how many miles I get from this tankful
Note my first post "Note FSI users this is not for you, keep yours running on the good stuff only, your cars need the extra RON and are very fussy on fuel. " so thanks for the info Dave but I would splash a bit more cash on that nice FSI of yours!
 

Robthebank

Member
why don't you run it on veg oil and not worry about fuel consumption @70p per litre :)
Now I was looking at that, are the fuel lines and pump OK with virgin Oil? I see a warning about Bio but i guess that is due to the methanol. I seem to remember that the government dropped the need to pay duty for "personal use" is that still correct?
 

Robthebank

Member
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.
So Fuelly now back up and running (see signature) that confirmed that my DIS was accurate, Fuelly actually showed a slightly higher average MPG but that just means I fitted a little less in the tank this time, as I said may take a couple of tanks for that inaccuracy to be removed from the average figure.
 

Dave Kelas

Member
Note my first post "Note FSI users this is not for you, keep yours running on the good stuff only, your cars need the extra RON and are very fussy on fuel. " so thanks for the info Dave but I would splash a bit more cash on that nice FSI of yours!
I should have read your post more carefully lol.

I wouldn’t run on veg oil. Pump Deuse high pressure diesel fuel pumps are fussy. You will destroy it. Old low pressure diesel cars are fine but you’re going back to the 80s for that technology
 

damadgeruk

A2OC Donor
Now I was looking at that, are the fuel lines and pump OK with virgin Oil? I see a warning about Bio but i guess that is due to the methanol. I seem to remember that the government dropped the need to pay duty for "personal use" is that still correct?
Yes, no duty required on veg if using <2500 litres.
 

Edwrai

Member
I should have read your post more carefully lol.

I wouldn’t run on veg oil. Pump Deuse high pressure diesel fuel pumps are fussy. You will destroy it. Old low pressure diesel cars are fine but you’re going back to the 80s for that technology
It would kill the fuel pump they cannot be used with SVO they maybe may not die as quick with converted stuff but they pump really doesn’t like veg


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Very difficult to say for sure on fuel consumption, but I'm starting to think that Tesco diesel is ok but Morrisons isn't. The engine seems to run more smoothly.
 
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