Fuel gaugeEnlarge Photo
3. Diminishing returns
The sort of person interested in a high-mpg car is likely to own one already.
Unfortunately, this means they're already using relatively little gas, and even fairly large increases in economy would save proportionally very little additional fuel, compared to someone moving into a moderately economical car from an inefficient one.
An example: A driver doing 12,000 miles per year in a 30-mpg car will use 400 gallons, costing just under $1,500 at current fuel prices.
Should they trade up to a 50-mpg car--a Prius, for example--fuel use will fall by 160 gallons, and their gas bill will drop to less than $900--a $600 saving.
But a second driver who trades a 50-mpg Prius for our hypothetical 70-mpg fuel-sipper makes seemingly the same 20-mpg jump. This time, though, the overall saving is only 70 gallons--cutting the gas bill only $250.
It's why we've said that miles per gallon is a stupid way of rating a car's efficiency. It isn't linear, so doesn't illustrate the cost reductions of moving from one car to another.
Granted, a driver trading from say, a 35-mpg car to a 70-mpg car will realize some hefty savings: Fuel use is halved, as are the gasoline bills.
But for those already driving an efficient vehicle, savings could be minimal. Particularly if they already own that 60-mpg first-gen Insight...
2014 Nissan LeafEnlarge Photo
4. Electric vehicles
This is the real "elephant in the room" as far as a hyper-economical small car is concerned.
It wouldn't be hard to make a fuel-efficient small car for a reasonable price. It wouldn't be too difficult to make it a little more practical.
But the sort of people you'd aim it at--the kinds of buyers really intent on saving fuel and reducing oil use--may already have moved on to electric vehicles.
Electric cars don't suit everyone, naturally. But if you're making that much effort to buy a car that does 70 or 80 mpg, with the latest technology, you may want to just skip the gasoline-powered middle-man and get a pure EV.
Why spend extra to get an ultra-efficient fuel-sipper, when you could buy a car that doesn't sip fuel in the first place?
Unless you regularly do longer journeys, it would be a no-brainer for eco-conscious buyers.
Nonsensical... but still appealing
There are still some buyers for whom our hypothetical car would be ideal.
This author, for example, tends to drive only longer distances--making electric cars impractical.
A 60-70 mpg Insight is currently ideal, for that reason--but a 70-80 mpg modern equivalent with better sound insulation, the extra surge (and response) of a more powerful (yet more efficient) hybrid system would be even better. Throw in a modern infotainment system and it'd be perfect.
Unfortunately, drivers like that are few and far between--not really numerous enough to present a solid business case to a major automaker.
So while we can expect regular cars to become more economical as the years pass, don't hold your breath for a true, affordable successor to the highest-mpg non-plugin the EPA has ever tested.