[bzzzt]

Some countries literally subsidize gasoline, but even if your country does not it probably supports oil companies with tax breaks ('creating jobs'). There also are lots of untaxed externalities like global warming and exhaust pollution.

[graemep]

Untaxed externalities are very different from subsidies. We do not generally tax externalities.

I live in the UK where we pay heavy taxes on fuel and we pay higher taxes on vehicles with higher CO2 emissions.

[bzzzt]

They are not so different: it's the same private/public money dynamic but money flowing in different ways. For consumers it doesn't really matter if it's a tax or 'mandatory levy'. For instance: in the EU it's mandatory to pay for disposal of consumer goods, which is priced in with every purchase. That's as close as a 'disposal tax' as you can get.