99-octane fuel proves more efficient than regular unleaded
10 December 2008

The benefits of high-octane unleaded petrol outweigh the extra cost of the fuel, expert tests have concluded.

Thorney Motorsport compared two identical Vauxhall Astra VXRs on the same routes over a four-month period.

Standard Tesco unleaded was used in one, Tesco's 99 Octane brand in the other.

The car running 99 Octane averaged 25mpg during the tests, while the lower-octane fuelled car returned 22mpg. That's an overall improvement of 14 per cent.

Daily dyno tests also revealed that the VXR running on 99 Octane produced 252bhp on average, compared with standard fuelled car's 235bhp.

Thorney Motorsport concludes that it's worth paying extra for the Tesco 99 Octane fuel, because you can go further on a tank.

However, high-octane unleaded is known to have a greater effect on heavily tuned and turbocharged cars like the VXR than it does on lower-spec, naturally aspirated models.

Will Powell

Find an Autocar car review

Driven this week

Join the debate


10 December 2008

This is a win-win situation. How else can you increase your car's power output without any requirement to inform your insurance company? Is there a website that is testing cars to enable us to look up our own cars difference?

It might be as well to play this fact down though, or 'what fuel do you use' will end up as a standard question asked on insurance proposal forms. Disreputable companies may take to sampling fuel after accidents when looking for get out clauses. I can see some Barrister coming up with the phrase 'chemically modified'. (The car, not the driver).


10 December 2008

Anyone with an ounce of petrol in their blood will already know this, especially if they run a high performance car.

My Integra will return in the region of 5/6mpg difference in fuel economy and runs cleaner, smoother and a lot quicker with it.

The important caveat is the "high performance vehicle" part of their survey. Certainly 99 makes no where near the difference on something like my basic 1.6 Civic, and 1 maybe 2 MPG improvement on the fuel consumption.



It's all about the twisties........

10 December 2008

A few years ago i went to the us with a mate and we did a sort of road trip thing, we had some awful pontiac witha 3.8 V6. we only used regular once, i think it was 85 octane (water would have been better) we then would only use the highest we could find and it made a huge difference. We passed on using 115 octane available at some hicksville gas station though, would probably have blown the thing up.

10 December 2008

Higher octane= Higher mpg?.

But I remember a few years ago one of the car programmes on tv tested a 100+ octane fuel that I think Tesco had introduced to a select petrol stations by using it in a range of cars but found very little difference....

I know it makes a difference in Japanese cars as thier engines are developed with the home market in mind and they have higher octance fuel as standard at thier petrol stations.

Also more importantly, does the increase in mpg justify the additional cost?, as there is a 7-10p per litre difference in cost.

10 December 2008

Using high octane fuel won't blow up your engine - the octane rating refers to the fuel's resistance to pre-ignition (knock/pinking). High-octane fuel doesn't neccessarily contain any more energy than regular, it allows the engine to produce more power by running at more favourable boost/mixture/timing settings.

Any car with a knock sensor (if the compression ratio is high enough in the first place) should be able to benefit from higher octane fuel, as the ECU can monitor what's happening and optimise the engine parameters as far as possible without inducing knock.

My 1.6 focus (which has a knock sensor and 11:1 compression) does seem to return a few MPG better on a run with 99 octane. My Saab 9000 turbo absolutely required it for full boost to be available...

10 December 2008

my 1992 saab 900 turbo ran much better on super unleaded. my 2005 honda accord 2.0 is much smoother in the vtec zone when running on super. my 250 cc fuel injected vespa gts is much more responsive on the good stuff. i'm convinced.

11 December 2008

Not saying I disagree with the findings, but I did notice that "Tesco 99 Octane" is a sponsor of Thorney Motorsport, who conducted the experiment.

12 December 2008

I've got a Subaru WRX PPP, 03 plate. I've run with normal petrol and with Optimax, compared results from both. Gave each a few tanks to bed in before monitoring over a few fill ups what the MPG was during a normal week's worth of driving.

Optimax gave better MPG - 26 vs 22.

Optimax has better torque at lower revs.

Optimax felt more powerful at higher revs too.

Optimax has now been replaced with V-Power, which gives similar results.

Tesco 99 doesn't have the same torque at lower revs, and while I didn't do such an extensive test it didn't seem to give the same MPG as the Shell product either. Remember that Tesco 99 has a high bio-fuel content, so it's "calorific" value is lower. You get less bang for your buck! As for normal Super Unleaded at 97 RON, car runs better than 95 RON but not by much. The car is just so much smoother and refined when running on the Shell product. Plus, the extra MPG more than covered the extra cost.

I don't work for Shell, and these are just my own observations. Your experience may be different.

12 December 2008

So your an economical driver are you?, if you were you'd not be driving a high performance vehicle, you did'nt buy it to see how many miles per gallon you got , you bought it for its performance/ handling ect.Now i don't drive an eco car either (530i M-Sport,30mpg), but thats mixed driving, longer drives it does 34mpg on ordinary unleaded, i don' see the point in using higher octane fuel for such a small increase and now that petrol is down to under 89p per litre who needs high octane fuel now anyway.The best way to eek out fuel is be a bit less lead footed, change gear a the correct times, check yourtyre pressures are correct they have a big effect on mpg, these and a few you can come up with yourself will still give you what you want from your car and put a smile on your face when you want to be a bit of a hooligan......merry christmas to you all !

Peter Cavellini.

12 December 2008

[quote Peter Cavellini]So your an economical driver are you?, if you were you'd not be driving a high performance vehicle, you did'nt buy it to see how many miles per gallon you got , you bought it for its performance/ handling ect.[/quote]

As a Z4M owner, yes I am an economical driver. I didn't by a high performance vehicle just to be a cock, and while the performance and handling is everything I would expect it to be, I need it to return a certain level of economy too when, for example, I go on long runs (London to Menton, and back six times per year, around 800miles each way), using fuel like V-Power makes all the difference, as well as driving sensibly, having the car nicely set up etc. One doesn't need to nulify the other.

Add your comment

Log in or register to post comments

Find an Autocar car review

Driven this week