Ha ha seriously this is just a trial & error that i & my hubby done with the petrol stations here in Sri Damansara. Often we fill up out tank and end up losing half of it cause the owner put other stuff in their petrol. It's so obvious if you use your car for works cause you can see the tank just vanish like that.
So, Petron, Shell & Petronas here is so out of question. You can tell it's wrong when you smell the strong smell of kerosene of something when you fill up your tank. The stronger the smell the less petrol actually you'll get.
Out favorite petrol station now is Caltex owned by Haiza. Situated along the road to Sri Damansara Industrial area. There's no smell when you fill up your tank and it lasts us long. It's proven ^ ^
Next time you want to fill just smell it and see the different between petrol station ya..