My 25-year-old car gets 30+ miles to the gallon, far better than an F-series truck, which is the best selling vehicle in the US.

It's been 30 years since anyone sold a new carbureted production car in the US, for just as long cars have had OBDII, and it's been 50 years since cars were sold without catalytic converters.

There was a time, immediately after those technologies were developed, when older cars polluted significantly more than newer cars, but modern engine designs have been around long enough that cars old enough to be big polluters are expensive collectors pieces.

There may be an occasional car with a blown head gasket or piston ring polluting excessively, but they won't run for long in that condition. Thanks to CAFE standards increasingly limiting the availability of smaller vehicles in the US, the average 20-to-30-year-old gasoline engine probably pollutes less per mile than the average 0-to-5-year-old gasoline engine.