Can't see it delivering much performance increase for a bog standard car but I had a tuned Saab Turbo 9-3 (about 235hp from 150hp standard) and it loved the stuff.
It was noticably faster and held onto turbo boost for much longer. Regular 95 would cause the engine to 'pink' and the car would automatically retard the ignition to prevent detonation. Tesco 99RON had no retardation and full power all the way.
BUT it was a tuned engine with a turbo, can't see the benefit for a bog standard 1.6 16V though...
HJ, have you tried a tankful of Tesco 99 and compared it to Shell V-power ? Be interested to hear what your findings turn out to be.
Thorney Motorsport tested an Astra VXR with Tesco 95 and Tesco 99 petrol. They used 2 different cars and the results showed a 9% improvement in power and 10% improvement in fuel economy, that's pretty impressive. a900ss, your findings support those of Thorney Motorsport. They tested using 2 standard tuned Astra VXR's and then retested using ECU upgrades, both sets of tests produced significant improvements in power and fuel economy.
I just don't buy the 'engine works better at low speeds' argument. For mild acceleration and certainly cruising, even a modest engine should be operating at a moderate BMEP and shouldn't require any spark retard from the ECU. I just don't see how the octane could be beneficial.
It be of course that the fuel's calorific value is slightly higher, or that the burn rate is faster. Fast burn is very important to efficiency. Sadly people get very attached to numbers (like Ocyane rating) because it's easy to make comparisons. but there's a hell of a lot more to fuel that facile numbers.
or that the burn rate is faster. Fast burn is very important to efficiency.
Actually the burn rate is slower and more controlled, it is the slightly slower burn that provides the anti knock properties enabling the ignition to be more advanced. And the more controlled burn makes full use of the whole charge.
I remember that Honda had problems with "high octane " petrol when used in the 1960's on their 5 cylinder 125's which were reving above 20,000rpm. The high octane (probably 110 ish) burnt too slowly and restrcted the revs, so they had to switch to lower octane fuel with a faster burn.
I believe that the octane rating is far too crude a measure to determine the quality of a fuel and there could be additional useful information to help choice(apart from the usual BS rating).
On the other hand cars with actively managed closed-loop ignition timing might benefit at low revs, because at very light engine loads the fuelling might be very weak for better economy leading to detonation, which the knock sensors pick up and retard the timing - I suspect the difference will be tiny though.
A lot of normally aspirated Japs, Fords and Vauxhalls are actually optimised for 95 RON fuel so you're wasting your money with high octaine stuff. Turbo cars and most BMWs are optimised for 97+ octane fuel. Which is why it REALLY bugs me when the car mags routinely use (usually sponsored) super duper fuel (BP Ultimate, Shell Optimax etc) in their road tests - this favours BMW and will make their cars shine in terms of MPG and power/performance figures, both of which are reduced by running 95 RON fuel, where as your average Mondeo will produce the same performance and economy figures on "normal" juice or super brew.
Well MikeTorque, the admission of a loss of power and fuel economy on 95RON shows their specified power output and fuel economy for that (turbo) model is on super juice. Not surprising as the majority of (high boost) turbo-charged cars are set up the same.
Steve, the Vauxhall quoted power/torque figures for the Astra VXR of 240PS and 320NM are based on the use of 95 RON. If higher RON fuel is used then both power and torque are increased as well as a reduction in fuel consumption, see link below further details.
Apart from octane rating, does anyone know any other ingredient difference between Tesco 95 and 99?
Additionally, does anyone know the ingredient difference between the other premium products?
I'm not talking about advertising hype, but actual chemicals and their effect?
I would expect their concentrations to be secret, but I'm sure someone must have done chemical finger-printing on the various brews and published the data somewhere, though I've had no luck with the usual search engines. I probably need a specialist one(?)
An enhanced additive package; To remove existing deposits and help the engine to run more smoothly, Tesco 99 Octane contains an enhanced additive package with twice the protective power of typical 95 octane fuel.
Back in 2000 the A41.8Tavant quattro i had was designed to run on 98 octane, that gave 180 bhp along with 171 lb/ft.
However it could be run with a slight power loss on 95, which i used 90% of the time, i could never find out what the power loss was, but the performance gain was only occasionally noticeable, no difference was evident with economy, 25mpg round town, 32mpg on the motorway.
If you have a VAG car its worth checking the hand book, just to see what octane is recommended.
I only used the 98 when towing, but at 5 pence per litre extra at the time, for me the cost was prohibitive.
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