Petrol - 95 or 97?

[Colinn]

Can anyone tell me what, if anything, I will gain by using (and paying extra for) higher grade petrol? Is there any noticeable improvement in performance or economy. If not, what's the point? (PS: I drive a late model, three litre model 4x4).

 

[clivea]

Hi, my wife's SAAB 9000 turbo gives about 5mpg better (39mpg on run) consumption when running on Tesco Super, which contains bioethanol. With the slight increase in cost it is marginally above break even but the engine pulls well and smoothly.

 

[MONKEY1]

Colin,

The answer is yes and no. Scientifically according to the petrol companies and some of the more exotic car makers as well as a couple of engineering institutes the answers is yes.

Some of these "improvements" though cannot be noticed in reality. Significantly though I have seen three independent case studies which have all said that "Shell Optimax" does gives some benefit with no price cost.

You would be better I feel to insure you tyres run at the correct PSI as this can knock significant off your mpg with only being slightly under pressure. As can your choice of engine oil etc.

Monkeys Husband

 

[Steve L]

HI Colin.

You would be better off by paying attention to tyre pressures, a more fluent style of driving with less gear changes, removing the roof bars and not using the air con.

I get upto 6 Mpg more out of my 2 Ltr Laguna by staying in 5th gear approaching a roundabout and doing one gear change to usually 3rd to travel through. (block changing is the technical term.

Anticipating the traffic and generally bing more alert often pays dividends as you do a lot less downchanging and hard accelerating which again gobbles up petrol.

Another by product of sympathetic driving is less wear on the car. I get upto 40k from a set of front brake pads, twice that from the rear and around 100k from a clutch plate.

By no means am I a doddering fart on the road, far from it, I'm usually the one doing the long overtake of four or five cars doing 50Mph thinking they are the most efficient.

I don't know if you would recall the "Shell economy challenge" back in the 70's, but this was where people with ordinary everyday cars were given a measured gallon of petrol and then the winner was the one with the most miles on the clock. The favorite was a Citreon AX and it was driven very fast and hard through the bends and still did 70 miles on a gallon.

Performance and economy is not necesarily raw power or a meager engine, but how you use it.

Steve Ll

 

[vauxhall2]

keeps your engine clean,runs sweeter and therefore more effective.

 

[rob_jax]

Colin,

If the designers of your car fitted the engine with the necessary sensors and programmed the computer to respond to increased Octane rated fuel, then you should notice a difference.

The "Other Clive" wifes' SAAB 9000 Turbo will have a knock sensor on one of the engine cylinders, and the computer will advance the tuning until it detects the engine pinking, then detune itself just a bit - so it's always running on an optimum setting.

The two "improved" fuels - Shell V-Power and BP Ultimate - both Diesel and Petrol - can make a significant difference to fuel consumption and at the same time reduce emissions.

For instance my MB C270 CDI achieves 51+ mpg on standard Shell diesel, but 54+ mpg over exactly the same route when I use V-Power - same temperature and weather - car speed controlled by the speed limiter to 100 kph.

So I save about 6% on fuel consumption and the fuel costs about 6% more in Holland, but perhaps most important of all - the amount of diesel smoke is reduced by about half - and this engine is a clean diesel to start with. BP (Aral) Ultimate fuel gives similar gains.

But whether the improved performance or better fuel consumption are worth the extra cost when used in your 4x4 is something you'll need to discover for yourself.

I really agree with the people that recommended that you make sure that the tyres are at the correct pressure, correct engine oil - fully synthetic oil in the engine and gearbox makes a big difference to fuel consumption, and adopting a driving style that tries to be more predictive of what's going to happen ahead.

Robert

 

[RogerL]

You need to find out whether your engines ECU will re-map automatically for higher octane fuel.

If it won't re-map automatically then higher octane fuel is a waste of money.

If it will re-map automatically you'll get an increase in max power OR economy roughly equal to the increase in octane number.

If you don't use the extra power you could gain about 2% improvement in consumption, worth about 2p/litre.

If you use the extra power, you'll only benefit at full throttle, as part throttle performance can be achieved on lower octane fuel, just by opening the throttle a bit more.

Higher octane fuel will probably make your engine feel smoother.

I researched this some time ago, and keep my eye on price differentials, but came to the conclusion that my car is at full throttle about 1% of the time so economy would have to be the only justification - if the differential was less than 2p/litre I'd buy 98 fuel but as it's always more than that I'll stick to 95.

In some areas Tesco are selling a 101 octane biofuel, which would be worth paying 6p/litre extra for, but it's academic for me as they don't sell it in my area.

 

[Colinn]

Many thanks to you all for extremely enlightening answers. I feel I understand much more about the differences - and I will give a a tank of the higher octane a try and keep an eye out for the points you describe. At least I now know what I can reasonably expect. Tks again.

Colin.