This question requires the use of the market-based, tax incidence diagram discussed in class. The statutory incidence of this tax is on suppliers. The economic incidence needs to be determined by the relative elasticities of the demand and supply of gasoline in California. Thus, if the tax is eliminated, a greater portion of the benefit should also be enjoyed by demanders. Since the demand for gasoline, at least in the short run, is relatively inelastic, this tax, assuming no externalities, is fairly efficient.
Economists define an efficient tax as one that changes behavior little.
But, this definition assumes no negative externalities from gasoline consumption. Efficiency then needs to be considered in regard to whether consumption is reduced enough to internalize the externality. In regards to equity, economists usually measure it by classifying a tax as regressive, proportional, or progressive in terms of a person's income. Since poor people spend a greater percentage of their income on gasoline than rich, this tax is likely regressive in its income incidence and thus considered by many to not be an equitable tax. You have gotten yourself into a debate regarding whether the overall incidence of property taxation in the United States is regressive or progressive.