Fuel economy on super unleaded

[PaulMdx]

A while ago I said I would be tracking my fuel economy using super unleaded in my SLK. Graph will follow shortly, however in the meantime here is the difference:

March 08: 25.6 mpg
August 08: 28.2 mpg

That's over 10% improvement with an almost identical drive (to and from work, mixture of by-pass, town and country roads) and similar driving style (if not a bit more heavy footed).

I've seen consistently better mileage each time I fill up by about +0.4 mpg each time. If the improvement IS due to using super unleaded, I'm actually saving money by paying the extra.

Edit: I'm using Shell Optimax.

 

[psmart]

Winter and Summer will affect fuel consumption as well. I noticed in the A-Class that 95 Octane was best, followed by 100 Octane, then 97 Octane (super-unleaded) on the 1.4 Petrol. I couldnt work out why 100 would be better than 97!

 

[jibcl500]

Agree, Optimax always made a huge difference in the 911, better performance, MPG, and the car was smoother on it too.

jib

 

[NewMB]

On my Volvo's I always only used Super Unleaded (Shell Optimax) and it always made the cars smoother and being a tad more economicaly

 

[Paul S320CDi]

Sounds interesting. Is there a similar premium fuel for diesels? Do BP have a blue nozzle with some better diesel in? I can't remember

 

[3146bj]

Changing from standard unleaded to Optimax on the E280 gives an improvement from 10l/100km to 8l/100km. In the Discovery there is no improvement as the compression ration is too low to take advantage of the higher octane rating.

Optimax (or V-Power as it is now) also has a higher specific gravity (0.78 v 0.72) and later engine management systems can take advantage of this increase to meter less volume of fuel at a given air mass flow rate to achieve the same power output. Very simple really - the same volume of fuel is a greater mass and therefore higher energy content, so reduce the volume for the same energy available. Add in the benefit of slightly more efficient combustion due to the higher octane rating and even better economy is possible.

In time, the higher SG fuel will become the base fuel for all unleaded and the SG advantage for Optimax will disappear, leaving only the benefit of the higher octane rating - until the chemists come up with something even more clever!

 

[amwebby]

A while ago I said I would be tracking my fuel economy using super unleaded in my SLK. Graph will follow shortly, however in the meantime here is the difference:

March 08: 25.6 mpg
August 08: 28.2 mpg

That's over 10% improvement with an almost identical drive (to and from work, mixture of by-pass, town and country roads) and similar driving style (if not a bit more heavy footed).

I've seen consistently better mileage each time I fill up by about +0.4 mpg each time. If the improvement IS due to using super unleaded, I'm actually saving money by paying the extra.

Edit: I'm using Shell Optimax.

That works out to a maximum of less than half a penny per mile saving at 28.2 versus 25.6

At 0.4 mpg difference the Super is actually costing you 2 pence per mile more than regular.

 

[JEZ.S320L]

That works out to a maximum of less than half a penny per mile saving at 28.2 versus 25.6

At 0.4 mpg difference the Super is actually costing you 2 pence per mile more than regular.

He's probably using the same calculator that the Govenment uses to tell us that crime has gone down and that inflation is less than 4%

 

[psmart]

Optimax (or V-Power as it is now) also has a higher specific gravity (0.78 v 0.72) and later engine management systems can take advantage of this increase to meter less volume of fuel at a given air mass flow rate to achieve the same power output. Very simple really - the same volume of fuel is a greater mass and therefore higher energy content, so reduce the volume for the same energy available. Add in the benefit of slightly more efficient combustion due to the higher octane rating and even better economy is possible.

Makes perfect sense, but it would be a case of try and see on others vehicles unless we built up a list. On the A140, 97 Octane (Optimax) and 100 Octane (not sure its available generally in the UK yet) actually give worse mpg compared with 95 Octane.
Paul S320CDI - You do get V-Power diesel.

 

[jon_harley]

Another data point: I've seen about the same 10% improvement in MPG as PaulMdx when using V-power in my CLK320.

 

[PaulMdx]

That works out to a maximum of less than half a penny per mile saving at 28.2 versus 25.6

At 0.4 mpg difference the Super is actually costing you 2 pence per mile more than regular.

I'm not sure what calculation you're doing there..!

My thinking is as follows: I've gained a 10% improvement in MPG, but Optimax is less than 10% more expensive, therefore it's economic to buy Optimax.

The 0.4 mpg improvement has been incremental every time I've filled up (thus far), which isn't related to the actual cost saving I see.

 

[RichardSmith]

I tried V-power in my old SLK230 and it made very little difference. I have tried it a few times in my SLK350 and whilst the car runs no differently, there is a slight increase in fuel economy.

But then again, all my cars seem to get better fuel economy in general from Shell petrol over BP. (NB I only use Shell or BP in order to collect Pluspoints or Nectar points)

I do find that my 300zx prefers V-power or super u/l in the summer months. I know that turbos prefer colder temperatures; the boost pressure does drop a little when ambient temperatures get above 26 degrees. The higher octane fuels seem to combat this, helping to maintain performance.

Richard

 

[amwebby]

I'm not sure what calculation you're doing there..!

My thinking is as follows: I've gained a 10% improvement in MPG, but Optimax is less than 10% more expensive, therefore it's economic to buy Optimax.

I worked out a cost per mile based on Super and Regular based on the MPG you gave and prices today in my area.

Regular 1 litre @ 1.144 per litre = £5.20 a gallon
Super 1 litre @ 1.121 per litre = £5.51 a gallon

Regular @ £5.20 divided by 25.6= 0.203 per mile
Super @ £5.51 divided by 28.2= 0.195 per mile

 

[st4]

http://en.wikipedia.org/wiki/Octane_rating

Have a wee read...

 

[PaulMdx]

Regular @ £5.20 divided by 25.6= 0.203 per mile
Super @ £5.51 divided by 28.2= 0.195 per mile

So it's cheaper to use Super. Woohoo.

 

[amwebby]

That's what I said, half a pence cheaper. That is at those prices. Taking the higher prices I see elsewhere the differential disappears and actually goes into reverse, i.e. it becomes dearer. Swings and roundabouts.

 

[roofless]

calculators & anoraks even the odd graph if youre that tight buy a wee diesel & freeweel down hills

 

[psmart]

http://en.wikipedia.org/wiki/Octane_rating

Have a wee read...

Very good article, explains a lot. Here in Austria, Petrol is sold in 91 (Normal) and 95 (Super) and 100 (with a special name), and in Germany its 95 (Normal), 97 (Super) and 100 (with a special name). You also get 'Special Name' versions of 97 octane, so just buying a different octane is not really going to help, you have to buy the special name brands like V-Power to get the higher energy density and thus the higher mpg.

 

[roofless]

calculators & anoraks even the odd graph if youre that tight buy a wee diesel & freewheel down hills

or keep your car well serviced & check the tyres & you cant go wrong

 

[David Nock]

Just spent half an hour on excel to prove that (on the above figures) V Power is cheaper than Regular in terms of pence per mile. But I knew that already from my own experience with a petrol C180. 10% extra mileage for about 6% or 7% price premium.