How Come Hybrids Don’t Get Great Gas Mileage?

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Hybrids get pretty good – but far from great – gas mileage.

The best of them – that would be Toyota’s Prius – manage low-mid 50s. Most average low-mid 40s. Which is good, but far from spectacular. After all, 40-something MPG is only about 8-10 MPG better than many current-era non-hybrid economy cars manage.

It’s not that big a difference – especially when you factor in the difference in price.

So – how come? Why aren’t hybrid cars more economical? How come they can’t go farther on just the batteries? Why do they need an internal combustion (IC) engine at all? Couldn’t they be made simpler? Why the need for two powertrains – the gasoline-burning engine and an electric motor?

It’s a Catch-22 situation.

Without some way to top off the battery pack “as you go,” hybrids wouldn’t be able to go very far – due to the limitations of battery capability. Hence the IC engine, which serves as an on-board generator in addition to providing propulsion. The IC engine makes hybrids practical – which is essential for them to be successful as other-than-expensive toys (see electric cars).

Electric motors are in many ways superior to reciprocating, internal combustion engines. They are much simpler. They deliver immediate and abundant torque. And because there’s no need to convert up and down (reciprocating) energy into rotational energy, they can “direct drive” the wheels – without a transmission to leverage mechanical force.

But – Catch 22 – you need electricity to run the motor. Hence the battery pack. Which needs to be kept charged up.

Hence the IC engine.

This is why hybrids are more complicated than conventional cars – as well as more expensive. It’s also a big part of the reason why they’re not as gas-sippy (or even “electric easy”) as you might expect them to be.

But, there are several things that could be done to make hybrids much more efficient. Chief among these – lighten ‘em up!

Honda’s original Insight – made in the late ’90s/early 2000s – was capable of 70 MPG. It was a light two-seater. Most current hybrids are fairly large (mid-sized) sedans/hatchbacks and very heavy. An Accord hybrid weighs 3,550 pounds. The Camry hybrid, 3,435 pounds.

My 1976 Pontiac Trans-Am weighs only slighty more than they do.

Even the Prius – king of hybrids – weighs more than 3,000 pounds. This is about twice the curb weight of an original model VW Beetle.

Hybrids are heavy to a great extent because of government “safety” mandates – which of course conflict with the goal of making cars (and not just hybrid cars) more fuel efficient.

Nothing wrong with “safety” – but it’s not a freebie.

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