It has to be expensive enough to depress consumption and/or promote more efficient use. Countries where oil is expensive have better fuel efficiency, for example.

Doubling the price doesn't help much (inelastic). Look at countries with huge petrol taxes and they still use heaps: https://www.globalpetrolprices.com/gasoline_prices/

I'm in New Zealand, and plenty of us have serious gas guzzlers even though petrol is far more expensive than in the US. A bunch of Scandinavian countries are twice as expensive as the US.