Unleaded or Super?

Peeps

Saw this mentioned in someone's thread (apologies to the older (not by age ) members, if its been covered before)....

Given cost of fuel these days, and trying to make ends meet with a 2 litre GTI, I seem to be 'taking note' of all things that relate to fuel economy.

Example - I recently learnt that a double bubble screen gives less 'drag' and hence gives better economy (thanks to the member that posted this in a thread) Moreover - I very recently learnt that I had a double bubble on my curvy, thinking i didn't!!

Anyway.. to the point. I've always only ever used unleaded (both in the car and in the SV), has anyone used super unleaded and found a major difference?

is it worth it?

opinions and views appreciated.

[Biker Biggles]

I found that using BP ultimate seems to give slightly better mpg,but it probably does not give enough to justify the cost.However in winter I found that it reduces carb icing so becomes worth it then.

[Stingo]

I've been using super for about four months now and, whilst not doing the science, I would swear that I am getting more mpg than I was when I used the 95 ron.

My weekly fuel was always around the tenner region - now it's more like £8 to £10 pounds, dependant upon tons of variables of course. This week my fuel top up was about £7.65 at an esso station. Can't remember the price per litre, but as I say, I've not done the science, I just stick the stuff in!!

Hope this helps!!

I've done a bit of the science on my blog...

Averages:
BP Ultimate (97 ron):
Mpg 51.46 KM per Litre:18.21 Pence per mile:8.61 £11.87 137.7 miles
Shell Optimax (97 ron):
Mpg 52.87 KM per Litre:18.11 Pence per mile:8.27 £11.75 142.2 miles
Sainsbury's Super Unleaded (97 ron):
Mpg 51.56 KM per Litre:18.25 Pence per mile:8.12 £11.61 139.5 miles
Sainsbury's Unleaded (95 ron):
Mpg 50.37 KM per Litre:17.83 Pence per mile:8.24 £10.88 132 miles

So there is a difference but not much, also I had my carbs cleaned last month and its added another 7-10 per tank full.

I use this online MPG calculator, it very good. Just fill up to your rim, reset the trip, do the journey, fill up againt to the rim and take note of you mileage and used fuel.

ive noticed no diff so now i chuck in sainsburys cheap stuff.

[northwind]

Even if you get better economy- which is open to debate, myself I just don't know- it's not usually said to be enough to justify the price. Grinch's figures are good, but still not enough to really be cartain off since you'd need a massive sample to remove the other hygeine factors.

In winter, I use Optimax because it means I don't use so much carb icing additive. More than pays for itself there.

[Luckypants]

You will not notice very much difference in an SV as it has no knock sensor to help adjust the ignition timing to take advantage of the higher octane of 97 RON. So there will be a negligible economy advantage, but not great.

However your GTi will have a knock sensor and will be able to adjust the ignition timing to take advantage of the higher octane rating, resulting in more complete combustion and possibly a decent improvement in economy. You will notice a difference in power and torque in the car.

My old V6 Omega loved 97 RON (the higher the better) and around town almost justified putting it in, but not quite. I think it improved from 17 MPG to 20 MPG with super plus stuff.

Final thing, I notice super is only a couple of pence dearer than plain old unleaded in my local Tesco. It's cheaper than diesel ffs! So I would defo try it in your GTi.

Where i live we only get 95 octanes unleaded , and 98 octanes unleaded(super replacement) , im getting a slight better fuel economy on my SV with 98 octanes fuel , went from an average of 6.2L/100km(95oct.) to 5.8L/100km(98oct.) , considering that 98oct. only cost 0.02Euro more per litter than 95 ,the bike back fires a lot less , fells smother at low rpm's , im sticking with 98 from now on

[embee]

The higher octane fuels usually have a very slightly higher calorific value and also a very slightly higher density (by virtue of the specific hydrocarbons in the blend).

In other words, since you buy fuel by the litre, you get slightly more mass for your money, and each kg contains slightly more energy.

The effect of the 2 things combined is at best 2% more energy per litre , so Grinch's numbers look in the right sort of ballpark.

However the fuel costs something like 4% more per litre (in UK), so you only get about half your money's worth back. This is in an engine without the ability to optimise the settings to take advantage of the octane difference, as the others have said.

What you do find is that some engines respond better on certain fuels, it depends on the characteristics of each engine type. I have one car which although calibrated on 91RON (and no knock system/adaptive ignition etc), it does feel much better on Optimax or V-power fuel. It doesn't produce any more power or better economy that you'd notice, it just runs better. In the other car you can't tell any difference.

I can't say I've noticed any real difference in feel in the SV when I've tried Optimax etc, but I'm not riding it every day like some folk do.