Fuel prices in Malaysia are so heavily subsidised that it’s cheaper to drive across the border to Johor and fill up there (at a subsidised 60 US cents/litre) than it is to fill up in Singapore (US$1.57/litre this morning).
Unfortunately, Malaysia is now putting the kibosh on this locational arbitrage, by banning petrol stations within 50km of its borders from selling fuel to foreign-registered cars.
But if your car was high-mileage enough, and the tank was large enough, it’d still be worth the trip… assume you’re driving a 3.5-litre V6 Toyota Camry with a 70-litre fuel tank, which drinks about 9.8 litres/100km (24MPG for American readers, or readers still living in the 17th century). It’d cost you US$110 to fill the tank in Singapore – or you could drive to Malaysia, fill the tank for US$42, burn 10 litres ($6) of fuel driving the 100km round trip to the “free zone”, and you’d still save US$62/tank.
Or, how about a totally awesome 2008 BMW M5 – 18L/100km (just 13 mpg), 70-litre fuel tank? Again, it’d be US$110 to fill it up in Singapore, or $42 in Malaysia; the round trip would cost 18 litres ($10.80), and you’re still US$57/tank ahead. (And with the lax speed limit enforcement in Malaysia – erm, not that I’d know, people just tell me it’s lax, really truly! – you can use the M5’s V10 engine for its intended purpose on the way back.)