Gideon, I know in the end that any tax placed on the oil companies will likely be borne by the customers. That's a natural effect of the cause of taxation. It's an inescapable truth that most on the left don't understand, and it's one that the (supposedly and hopefully) bright people that run the oil companies would find a loophole or way around no matter how carefully crafted a bill or law would be created to be sure to tax only the oil company, and not have the tax passed along to the customers.
With that said, I don't believe that what Hillary is proposing is the same as what you are most directly aiming at, as gasoline taxes are typically paid at the pump, and yes, borne directly by the customer.
I don't disagree that the costs would impact the poor along the way, and I am not a fan of income redistribution in the style that Democrats typically use -- rob from the rich and give to the poor -- but perhaps that is somewhat needed here. We do need to get people to switch to more efficient vehicles. I'll admit, I've considered and am considering making a switch myself. I'd love to get something like the hybrid Honda Accord, or even better for me, a hybrid Toyota Highlander or perhaps a "green" Saturn Vue. Unfortunately the additional costs for the green versions of these vehicles are more than enough to make them unaffordable for me.
I bought a used vehicle, one that is a bit of a gas guzzler, that was bought based on affordability, size, roominess, ability to haul items and people as necessary. I'd be more than happy to get something used that is more economical and yet fits most of my requirements, but it's far too soon in the hybrid vehicle life cycles to find many used hybrids out there. What few are out there are still priced at a premium over non-hybrid vehicles, which means no matter what we're paying more to try to be green.
There have been various tax breaks in place for people that bought green. Tax credits, tax breaks, rebates, etc. At this point, perhaps we need more direct tax rebates for such purchases, tax rebates fueled by taxes raised on the backs of the oil companies. Tax rebates that are targetted to provide the biggest breaks and biggest assistance to those that take the oldest vehicles off the road, and those which need the assistance the most. (Needs tested, so to say).
Again, I'm not typically a fan of redistributing wealth, but there are times when we have to place the greater good ahead of the needs of the few. It's time that the oil companies and automotive manufacturers lead the way, even if they are forced to do it by helping to pay for it with our own money which is given back to us in tax rebates as we go and buy shiny new vehicles that do everything we are asking.