Economy versus Octane Rating

Have you got a reasonably late model car (EFI, unleaded)? If so, you might like to do some comparison tests as we did. Our car is a VL Commodore 3l auto wagon which happens to have the slightly higher performance Nissan engine usually fitted in the R31 GTS Nissan cars.

To make matters worse it has just about all the power robbing fuel-burning options available. Being a miser of Irish descent and having a background in motorsport I decided to investigate 98 octane fuels for improved performance. First step was to establish a reliable basis to work from, so the car (not just the engine) was thoroughly serviced and all worn or tired parts replaced. Not surprisingly the car was noticeably improved!

Second step was to build a dataset of recorded fuel refills, kilometres travelled, type of use (ie country or city, weather conditions etc) and cost per litre for each refill using ULP.

Third step was to repeat this dataset gathering, this time using PULP fuel. Note that in both cases we used a total distance of more than 8000 km to minimise any weird errors.

Analysing those datasets we were able to select about 3200 km from each where the type of use was a close match and this was then used to calculate an average cost per kilometre. PULP generally averages 5 to 6% more than ULP in SA but we achieved a REDUCTION in running fuel costs of approximately 2.1%!!

In addition there was a noticeable improvement in performance (acceleration and manifold vacuum at cruise). When we used the whole of each dataset the results only varied by 0.09% so selecting a match was a waste of time! 

Fourth step was to retune the engine by installing a 'performance chip' in the factory ECU and re-establishing the base settings of the engine to suit. The same dataset gathering was performed and the results analysed. Interestingly, there was a significant reduction in fuel cost compared to the baseline ULP data (around 8.9%) but at the expense of a $200 addition to the car and with some increased harshness to the engine characteristics.

My conclusion was that PULP was a significant advantage, but it really wasn't worth putting the 'performance chip' in the car ($200 buys a LOT of fuel when the gains are this small!). I removed the chip and returned the engine to its standard base settings Note that prior to the chip nothing was done to the car other than what would be required of normal thorough maintenance.

So, my recommendation is to take it step by step as we did and see if YOU might also gain from using PULP. If your car is specified in the factory data as having a compression figure over 9:1, has a turbocharger or supercharger, is a multi-valve or multi-cam or comes from a line of engines with a motorsport heritage then the probability is high that the results will justify the effort.

Art from Manoora, SA

Saving Money

I always watch the Motormouth prices for my chosen service stations for a few days leading up to when I want to purchase my fuel. That way, I can go to the cheapest station to ensure I get the best deal for my fuel.

I also follow the pricing trends and purchase my fuel as the price drops, and before it begins its rise again. So, in two ways I get to monitor and take advantage of the cheapest advertised fuel prices, sometimes within a few hours before the price rises by several cents a litre.

I'm saving between 80c and a $1 each time I refuel, so over the year that adds up to quite a substantial saving in MY purse. Thanks Motormouth, I truly appreciate the free service.

Shauna from Belmont, SA

Fuel Discounts

Join clubs like EasyFuel and Savesmart. Also make use of things like Servo Savers, Coles Express and for those in Victoria, Ritchie’s Stores as well. When you see a fuel discount at a supermarket being advertised, use that location for your shopping then you cut the price of your petrol at the same time.

In one case, by shopping at EasyFuel Participants you can get as much as up to 20c discount per litre. So take advantage of them.

Name withheld

Diesel Rip-off

Are people who drive diesel powered vehicles paying for the whole cost of Australia's involvement in Iraq or some other major project?

Perhaps we are subsidising LPG prices which are the lowest they have been for nearly twenty years. For a fuel that is lower on the catalytic cracking scale than petrol - it stinks!

Dianne from Crafers, SA

Fuel Saving Tip

It is possible to save fuel when you drive with you windows up as the Drag is reduced. This would only apply is your vehicle is air-conditioned. Also remove roof racks when you are not using them.

Name withheld

Iraq War

We all suffer from the very high petrol price and it wasn't that bad before the war in Iraq, so in my opinion the war on Iraq is the main reason for all this higher rate that we pay.

Ammal from Peakhurst, NSW

Rising Price of Fuel

The rising price is being blamed on the oil-producing countries and is correct up to a point. Listening to a Talkback on radio in Europe where we visited recently, I heard an Executive from OPEC say that they were releasing enough barrels of crude oil but there are not enough refineries to process it.

No money is being spent on updating equipment in the refineries and refineries have been closed down, e.g. the one here in South Australia. China has no refineries of its own and is dependent on other countries for obtaining petrol; it has increased its petrol consumption dramatically.

Consequently, the petrol companies are getting richer all the time.

Jim from GREENOCK, S.A