Petrol Tests


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With today's see-sawing petrol prices most of us have just one concern when filling up at the bowser and that's saving money. Even if sometimes it means wasting half a tank to find the best deal.

But does cheaper fuel necessarily mean the best fuel for your car or the most economical?

To separate myth from reality we decided to test and compare the performance of all the major fuel types. From the largest independent chain Liberty, to the big four, Caltex, Shell, BP and Mobil.

And the results will shock you.

We put each fuel through an identical test using the same car, a standard family Commodore wagon which we had serviced in advance with the team at Formula Automotive.

"Running all these different types of fuels can contaminate or coat the spark plugs of the vehicle, can contaminate the oil so what we're going to do here is we're going to drain the oil, renew the filter, replace the spark plugs and air filter and go through every bit of the vehicle to make sure it's spot on before we do these tests," explains mechanic and owner Nick Boffa.

Next we intended to fill up our jerry cans with a premium unleaded, a regular unleaded and an environmentally friendly bio fuel like an E10 blend.

But things didn't always go to plan.

Surprisingly, unlike other states, none of the major retailers in SA offer a clean green fuel with 10% ethanol, that is, apart from the Unleaded 94 (plus Ethanol) at Liberty which as it turns out also proved to be the cheapest.

There was a huge gap between the 94 at just under $1.30 and the dearest premium unleaded petrol at $1.51 point 9.

And that disparity was from fuels sourced within a 7 kilometre radius in the space of an hour.

Next we took our samples to our team of experts at the University of SA, to create and conduct our tests.

They had already built an electric car and a solar car. The challenge we set for Program Director Dr Saiful Bari was to build an external fuel device to show exactly how the fuel is being consumed.

With the device built it was time to back the wagon onto the rollers at Aussie Dyno and Mufflers and start pouring in the fuel and soon after the results began trickling in.

Lex Felix, an automotive expert and Metrologist conducted the tests.

"I wasn't aware that you were going to get the variety of answers you were going to get so I'm looking forward to the final results," says Les.

"For emissions, the ethanol blend (94) outclassed the premium (BP Ultimate) and regular (Caltex Vortex) unleaded petrols."

And who led the field for engine power and grunt?

The much hyped high octane blends performed well at low speeds but were virtually on par with the rest of the field when it came to normal cruising.

So overall which fuel gives you the best bang for the buck?

The BP regular unleaded 91 outperformed even it's own higher octane blend with the lowest consumption of fuel, followed by the premium unleaded of Shell and Mobil 8000. Shell's regular unleaded rated fourth and BP's high octane fuel Ultimate came in at number 5.

Despite the surprise outcome, in the long term mechanic Nick Boffa says he'd rather pay 20 percent more for the premium unleaded brands because the real saving is in the wear and tear of your vehicle.

"We've had positive feedback with the higher octane fuel and what they do is they come back after and they do say yes we've had a result, we've gained i.e. better fuel consumption, more kilometres to the tank which puts money in your back pocket," says Nick.

The final results are:

BP unleaded regular
Shell V Power
Mobil 8000
Shell unleaded regular
BP Ultimate
Caltex Vortex 98
Mobil 2000
Caltex Vortex regular unleaded
Liberty PremiuMax
Liberty regular unleaded
Liberty unleaded 94

Report on test of Holden Commodor VY Station Wagon 3.8 litre with different types of petrol
The Holden Commodor VY Station Wagon 3.8 litre was tested with the following fuels on 7 November 2008:

  1. Shell Unleaded Regular
  2. Shell V‐Power
  3. BP Unleaded Regular
  4. BP Ultimate
  5. Mobil 2000
  6. Mobil 8000
  7. Caltex Vortex Regular Unleaded
  8. Caltex Vortex 98
  9. Liberty Regular Unleaded
  10. Liberty PremiuMax
  11. Liberty Unleaded

The tests were carried out on a chasis dyno at various throttling settings. For each fuels the setting were same. The power and fuel consumption were
measured. However, it is important to mention here that the results are obtained for Holden Commodor VY Station Wagon 3.8 litre car. Other cars may
perform differently.

The findings were as follows (as can be seen from the figures shown in the next few pages):

At a speed of 50 kph and 10 kW power which is the most common driving condition of this model vehicle: (source: Aussie Dyno Muffler and Brakes)

� When running the vehicle with premium fuel, the increase in power is less than 2.5 % for BP and Shell. All other fuels are less than 1% or same.

� The fuel consumption reduction for premium fuel is less than 2% for BP and Shell. All other fuels show reductions less than 1%.

� The power produced by the Liberty Unleaded (Ethanol based) fuel is similar to Liberty Regular Unleaded fuel but the fuel consumption of Liberty
Unleaded (Ethanol Based) is about 2.2 % higher than Liberty Regular Unleaded fuel.

Considering the price of premium fuel which is more than 6% compared to the regular unleaded fuel, the reduction of fuel consumption which is less than
2%, there is no real cost benefit using premium fuel. However, the test shows that at low speed there is a gain in power which is why people may feel that
the vehicle has more power. However, at cruise speed or the most driven condition, there is little gain in power.

When comparing the performance of all types of fuel available from different petrol station, at a speed of 50 kph and 10 kW power which is the most
common driving condition of this model vehicle: (source: Aussie Dyno Muffler and Brakes), the following conclusions can be drawn (as can be seen from
the figures shown in the next few pages):

� The variations of power produced are less than 4%.
� The variations of fuel consumption are less than 7%.