In Australia, some of the supermarkets gives a fuel voucher for a discount of $0.04 per litre at its affiliated service station. The two major affiliations are Coles with Shell and Safeway with Caltex. As our car has a tank capacity of 159 litres, we usually try use these vouchers as much as possible. To get the discount voucher, your grocery bill needs to be $30 or more for a single transaction. (I have seen shoppers separating their grocery purchases so that they can get more than one discount vouchers!)
I have always wondered if these vouchers actually save you any money?
Last night, I was filling up my 4wd at the local petrol station. This time, we haven't filled it for a couple of weeks and the tank is running quite low. With the price of diesel at about $1.24 per litre, it would cost $197.16 to fill the tank right up.
However, with the discount vouchers, there are several conditions.
- A single transaction can only be use for 150 litres of fuel.
- The voucher has a validity period, usually 1 month.
So as I was filling up my 4wd last night, I noticed a sign at the bowser saying that if I spent $5 in -store, I get a further $0.04 per litre discount. This gives me a total discount of $0.08 per litre.
Working through the maths,
Maximum saving is 0.08 * 150 = $12.00
Purchase to get extra $0.04 discount = $5.00
Effective saving is 12.00 - 5 = $7.00
This is good news as it would be worthwhile for me to spend the extra $5 in-store to effectively gain an extra $1.00 saving.
However, if I spend more than $6.00 in-store, it would be better if I just stay at a discount rate of $0.04 per litre as my saving would start to diminished.
So I guess that next time I rush in-store and purchased a chocolate bar and a bottle of soft-drink for the extra discount, I need to be careful not to spend more than $6.00.
Around the net, I found the following resources for saving fuel on cars.