>If people stopped buying things from far away that aren't really really necessary, maybe that will also reduce fuel use.
From what I understand, shipping long distances is super efficient per unit goods transported; the ship that drags whatever it is you buy across the ocean produces less carbon (per unit transported) than the truck from the port to your store, which emits less carbon per unit transported than your car going from the store to your home.
If you want to save fuel, argue for good public transit, higher density housing and mixed use zoning. Or, more controversially, perhaps look into efficient delivery services that deliver a lot of groceries to people in the same area.
I mean, to be clear, I'm not saying that pollution caused by larger transport should be ignored; it's probably easier to deal with pollution on a giant ship than on a thousand little cars, but my point is just that you should go after the biggest problem, that we live in low density areas and drive everywhere.
Note, people say there are a lot of economic arguments for buying local, though I personally think that is harder to analyze than simple carbon emissions, and I'm not addressing that here.
http://www.cleanmetrics.com/pages/ch9_0923.pdf
"Figure 9.3 also shows that the most energy-intensive transit link is often the last one–driving to the store. This is not surprising, because other studies, such as those by Browne et al. (2005) and Van Hauwermeiren et al. (2007), find that this link canbe the most carbon intensive even in European countries where consumers are tra- ditionally more energy conscious than their U.S. counterparts."