Can higher octane fuel boost your mpg?

[Fallguy]

Well I have only had a couple of tanks to compare with, and snow obviously skews any results, but from what I can tell super unleaded actually lowered by mpg rather than increasing it...

The 2 mostly full tanks of super gave me 40.66 and 40.78 mpg, whereas the last tank of mostly leaded returned 45.6 mpg and the tank before I filled up with super gave me 43.1 mpg.

Slightly puzzled as to why the results are so bad, unless the engine remaps the fuel injection to use more fuel with a higher octane tank. That would explain why the car felt more sporty.

Not sure I want to repeat the test now - given the extra cost of super and the lower mpg it will cost 2 to 3 pounds more per tank, and thats at current fuel prices!

[IanLorenc]

Sadly - whilst not wishing to call the integrity of your friend into question - I seriously doubt that switching to a higher octane fuel alone would really make that amount of difference...if any at all.

Erm. Okay. Cut me a large slice of humble pie, coat it in custard and consider this post an apology.

My brother recently tried Shell V-Power (99RON) in his Fiesta ST. He initially reported a slight improvement in throttle response and low down torque. Strangely though (considering he'd been "trying it out", looking for performance gains), he's reporting that the car also seems to be doing more to the gallon than normal, with more miles passing in relation to fuel gauge position.

I am thinking about making my next two or three tanks Shell V-Power, just to try it. Though I have looked in my handbook and it states:
Fuel: 95 Octane*
*98 octane can be used though there are no significant benefits

This must mean that my car doesn't have an anti-knock sensor and cannot take advantage of the extra octane. My brother - who gave me my car - said he'd tried Optimax in it (which is what V-Power used to be called). He didn't notice a power difference but felt it ran smoother. Unfortunately, he wasn't that into economy back then (still not that much now!) so couldn't say if it was more economical.

This is a good video from Fifth Gear about higher octane fuels:
http://www.youtube.com/watch?v=dDHwCWdrtdg

[IanLorenc]

V-Power update.
Despite the handbook telling me that my car would see no benefits from higher octane, I can report after a couple of tanks of V-Power, throttle response was improved and the pick up was generally perkier. I'm not going to make a ridiculous claim such as it felt like 5bhp extra across the rev range but I suppose the best way to describe the difference, is the difference between driving with a completely full tank and an almost empty one. That slightly leaden, weighed-down feel of a full fill-up against the friskier feel of when you're near empty.

However, unlike my brother which I shall explain below, I saw absolutely diddily squat difference in economy. On the next couple of tanks, I will try ordinary Shell unleaded instead of V-Power. I used to fill-up at Sainsbury's, which of course is BP supplied and it seems that no one on the internet (even before their current woes!) has a kind word to say about their fuels.

My bro - the lucky dog - has managed to get the holy grail of the same slight performance improvements I've described above AND increased economy. I can vouch that his driving style has not changed but he gets about 4-6mpg more on V-Power than on Sainsbury's 95. He used to get early 30's but now gets late 30's and has even got it over 40 once. Doesn't sound like much but for him, that's an achievement. Mk6 Fiesta 2.0 ST BTW.

Any one else dabbled in higher octane fuels? Apparently, most German stuff is supposed to run on the higher grade anyway.

[frv]

Any one else dabbled in higher octane fuels? Apparently, most German stuff is supposed to run on the higher grade anyway.

I keep meaning to put some 'better' diesel in but end up filling up at the cheapest place - usually a supermarket, occasionally ESSO or Jet.

[IanLorenc]

Don't get much of a choice with diesel. Correct me if I'm wrong but I believe there's only BP Ultimate Diesel and Shell V-Power Diesel out there.

In a slightly different vein, Superchips offer a guarantee that you will save fuel with their turbo diesel remaps or your money back. However they don't specify what this kind of saving may be, thus allowing you to approximately calculate how long it would take to recoup the £399 price tag through this saving.

http://www.superchips.co.uk/curves/accordicdti.pdf

[frv]

In a slightly different vein, Superchips offer a guarantee that you will save fuel with their turbo diesel remaps or your money back. However they don't specify what this kind of saving may be, thus allowing you to approximately calculate how long it would take to recoup the £399 price tag through this saving.

Ouch - If it got me 10% better mpg it would still take over 5 years to get my money back

[IanLorenc]

Okay, so maybe a viable proposition if it works as claimed and you're only interested in a good hypermile headline MPG figure.
Not so good if you actually to save money and not just as a fun hobby/challenge.

[Fallguy]

I guess the value in getting chipped would be higher if you do large mileages (e.g.airport taxi drivers, or delivery drivers). When I was doing 40000 a year for work the chip would have paid for itself pretty quick even with the lower fuel prices.

[Karl]

Chipping is a double edged sword if you ask me. I do agree that a decent fuel map with more power and torque will increase your MPG a little ... BUT

Often the other engine components are not sufficient to cope with the increases in power often leading to self destructing clutches and dual mass flywheels. I was tempted to remap the VRS to a healthy 170BHP and a shed load of twist but the talk of £1000 bills for new clutches and DMF don't particularly appeal to me. Also - temptation would most likely set in and increase the amount of time I would spend "enjoying" breaking my car from the inside and doing 10MPG while at it.

Personally - I'd rather just upgrade the man behind the wheel and loose a couple of stone!