E10 has just under 97% of the energy of E0 so fuel consumption will suffer accordingly.

Octane rating has no bearing on energy content.

 

That knock sensor is there for a reason. The fact that ie is an indication that the manufacturer expected/know there on publicly available (usually 95) petrol engine knock can act and that is harmful to the engine and the environment. So is there a knock sensor on. It is usual at such engines that there can be a higher efficiency than a gasoline with a lower octane rating.

 

This all true, but it's more correct to say that the knock sensor is there to protect the engine from damage due detonation if and when fuel of a lower than recommended octane rating is used. As we've read above, it's quite common to see owners using 89 or 87 AKI fuels here.

Jaguar and all OEMs are obliged to submit test results for pollution and economy certification prior to vehicle release to the public. Part of the data submitted is the octane rating of the fuel used during the testing. It appears that the Euro version of the car was certified on 95 RON. That also confirms that the advertised horsepower/torque figures as well as fuel consumption and emissions were based on this fuel.

My point is that using the rated fuel does not infer that the engine is experience detonation during regular use, nor that higher octane levels will return improved power or consumption numbers. Most cars show no improvement whatsoever when using such fuels.

 

Experience and measurements say more than theory.

Your ECU keeps all kinds of tables with all kinds of values. Including tables with knock sensor values and all sorts of other dates. A fuel with a higher octane will have a higher ping border and then the ECU itself set.

 

I'm going from experience and measurement just as much if not more than from theory. None of the above is theory, it's fact.

For an ECU to choose a different table to avoid detonation (knock/ping) the knock sensor must first detect detonation. If there is no detonation on a given fuel there is no point using fuel of even higher octane as the ECU will not choose a different table. This presupposes that there are more aggressive tables in the first place.

There is little or no data supporting use of higher octane fuels on newer Jags as they do not detonate on the recommended 95 RON fuel. Your findings on particular your car are a surprise to me and contradict the findings of owners of similar vehicles.

 

The ECU will always let the ignition take place against the knock/ping border. When the knock border comes later, the ECU will bring the ignition earlier, resulting in a more efficient consumption.

 

I guess we'll have to agree to disagree.

 

Over the years I have read many publications trying to tell if using fuel with a higher octane rating (or an more expensive lubricant) has any real advantage. Here is just one example.
Regular Versus Premium Gasoline
The common conclusion, supported by scientific validations, is no.
Two of my collection are pre-1995 cars, so I occasionally used cheaper fuel to try to see the difference in terms of efficiency and punch, and didn't. However, as consumers, like many others I am more persuaded by periodic promotions at fuel pumps offering higher discount in higher-priced fuel. That may be the secrets of modern energy giants. They add 3 cents worth of additives to regular fuel to claim 45 cents more in price than regular and this makes sense in actual sales. It may be that there is some difference but the gain is not worth as much as the higher price paid. What really matters is that consumers feel the difference and are happy with their choice. Period.

 

Experience or just believe everything they write?

The ECU in European cars is not the same than the ECU in U.S. cars. Maybe that makes this difference?

 

I believe that there is some difference and whether it is really worth the extra cost per litre is really up to the individual. To me after discount, the premium fuel is very close to regular so I still buy premium. Also, the motoring culture and experience in each region can be different due to a host of factors. However, consumer behaviour would be similar.

 

Although rather basic and simplistic, I see no errors in the article. It certainly matches my experience.

Is this factual experience or just a guess?

 

Environmental standards/requirements in the US are much higher than in the EU.

 

The X300 has a table of advance values for various load and rpm conditions, and the knock sensors can retard the timing from this value if knock is detected. However, the ECU will not advance past the table values to take advantage of higher octane fuel.

So for a car in new condition, there is zero advantage to using more than 95 RON/90AKI fuel. As cars age and deposits build up, the engines octane requirements may increase for whatever reason. Burning oil is one. In that case a particular engine may need more than the design octane to prevent retarded timing, but this shouldn't be extrapolated to saying that there is a general advantage to using higher than design octane fuel.

In some situations it's possibly to use less than design octane and not have the timing retarded, such as at high elevation in cold weather.

 

In fairness, the European cars have 2 O2 sensors, Canadian/US cars have 4 to make them OBDII compliant. Canadian and US cars also have EGR.

 

Jagboi has put his finger on a key point: the car can only take advantage of the higher octane of a fuel if the ECU has an appropriate "map" to allow it to do so. Similarly, it can only adapt for lower octane fuels as far as the available maps permit. I would hazard a guess that Jaguar built in maps to accommodate the vast majority of situations that the vehicles were likely to encounter around the globe, and married these up with the various market specific emissions regulations.
I have no doubt that the UK 95 and 97 RON fuels are catered for by the standard maps, and from my own experience with my XJR, I would conclude that the difference from the driving seat is extremely marginal. I can just about convince myself that the car runs more sweetly and on lighter throttle openings with 97 octane, and maybe even manages 1mpg better (perhaps not so trivial when you are averaging 20mpg!). In truth, I doubt I could detect a difference if someone else had fuelled the car and put in 95.