Cheaper petrol in Japan than Singapore

The above is the receipt for the petrol we bought from Enejet petrol station. We filled up the tank with 30.7 litres of petrol (regular) and the cost is 4,177 Yen which is the equivalent of S$51.56 ($1 = 81 Yen and divide 4177 by 81 will give you $51.56). Therefore, a litre of petrol in Japan is $1.68. The regular petrol at a pump in SG is $2.19 per litre and the difference is 51 cents. For me a it's a savings of $15. The petrol in Japan is cheaper than in SG due to the lower tax here. If petrol is cheap then most of the necessities of life are less expensive.