To find out if all fuels are created equal, we put six petrols to the test using two vehicles strapped to a chassis dynamometer.

Chassis dynamo-what? Well, it's a fanciful name for something that measures actual power output at the wheels. It is more meaningful than measuring the output of engines themselves.

We conducted our test using a dynamometer with the help of a technical team. Both were courtesy of Subaru distributor MotorImage, a company which takes performance seriously.

The test cars were a Subaru Impreza 1.6 and a Subaru WRX 2.5 turbo. These all-wheel-drive cars were also provided by MotorImage. Each test run costs around $100, but the distributor waived that for us.

Costs aside, there was the time and effort devoted to the experiment. The exercise spanned over a week because each fuel on each car was tested three times to arrive at an average. And the facility had paying customers to attend to in between.

The cars had to be drained of fuel and refilled, strapped on to the dynamometer and unstrapped and, of course, we had to go buy the fuels.

Life! was there to witness the procedure, and this is the first time a local newspaper has done such an exercise.

We picked 95-octane samples from Caltex, Shell, Esso and SPC. We also had Shell V-Power and Caltex Platinum - two ultra-premium 98-octane grades.

Space does not allow us to reproduce 12 charts and sheets of data here, so we've distilled the numbers to tell you how each fuel performed under different situations.

As you can see from the table, the findings are interesting. The ultra-premium petrols did not top the power charts anywhere.

Of course, the caveat here is that the two cars tested are not representative of all the cars on the road. At best, they are rough proxies, so your car may not yield the exact results.

The tests show that if the 1.6 is driven by someone who is seldom in a hurry and is mostly lightfooted, then Esso's 95-octane grade is best. If on the other hand it is piloted by someone who fancies himself a driving ace, Shell's 95 is the juice of choice.

With the 2.5 turbo, 95-octane grades from Caltex and SPC seem to do the job well for relaxed drivers. And Shell 95 serves the maniac behind the wheel of this car best, too.

One more thing. The performance of each fuel across the rev range may differ somewhat as actual output is never a straight line plotted in glossy brochures.

Torque is also not expressed here, but some graphs show the V-Power-fuelled WRX climbing more steeply from 2,000 to 4,000rpm.