More than you think. A hybrid car gets more mileage out of its engine for two reasons:

- regenerative braking reduces the efficiency penalty of city driving. While a normal car sees a 25-30% mileage drop in stop-and-go traffic, a hybrid sees about 5-8%.

- the actual engine is more efficient! The gasoline engine in hybrid vehicles usually replaces the Otto cycle with the Atkinson cycle. The latter is more efficient but has lower power, which in hybrids is compensated by an electric assist that turns on when accelerating.

http://en.wikipedia.org/wiki/Atkinson_cycle

By taking these two effects together a non-plug-in hybrid can reduce fuel use in a city driving condition by more than 40%. I didn't make that number up: the 2019 standard Camry has 29 city mpg, while the 2019 hybrid Camry is rated for 51. The hybrid uses 56% as much fuel as the conventional engine! With a plug-in hybrid that can drop even lower.

Unfortunately the marketing around all of this was muddled and most consumers have never heard of the Atkinson cycle. The original hybrids (Prius, Insight) were molded for a Japanese market, where simple and cute is a winning proposition, but American gearheads thought it looked and drove like a toy, a perception which was compounded by the fact that early hybrids made self-maintenance nearly impossible. Just replacing the 12V battery on a Prius is a major pain (speaking from experience!). Atkinson hybrids quickly became associated with a certain type of person and, for a while, many/most car geeks thought the real efficiency breakthrough were the German companies' maintenance-friendly and appropriately-scented turbodiesels, and we all know how that turned out. Hybrids have never captured more than 3.2% of the US market, but even if no highway-viable electric cars appear, a switch to plug-in hybrids could erase more than half of car-related GHG emissions.

I know all of this mostly because of one very old and very stubborn former engineer who was impervious to every kind of advertisement and cultural stereotype, and who studied the technology in the Prius and bought one new in 2009. Everyone else in the family made fun of him, but Grandpa just didn't care, and raved about the Prius to anyone who would listen. Most of us, including me at the time, believed the meme that Atkinson hybrids were a marketing gimmick and only relevant if you drove in the city often enough to take advantage of the regenerative brakes, and anyway, turbodiesels were the future. Grandpa didn't live long enough to see himself get proven right, but I still drive his car.

As a(n obnoxiously outspoken) 2016 Camry Hybrid owner, it's true. On highway it usually gets ~40 MPG. Below 45 MPH the engine can shut off, and often it coasts along, only using the engine to accelerate or go uphill. My Costco route consistently gets 45-50 MPG, and I use about 28 gallons of gas to go 1,080 miles a month.

Long term, I'm hopeful to replace the NiMH battery with lithium and a plug-in charger.

He didn't say it was due to more efficient motors. Just compare the average MPG of the cars on US roads, running on subsidized gasoline, vs. those on European roads, running on heavily taxed gasoline.

Gasoline in the US is taxed not subsidized.

An interesting question for this is will governments start with 'electricity tax'. There will be a ~$40bn revenue hole from cars swapping to electric in USA. Even proportionally more in Europe and Australia where the fuel taxes are much higher.

https://www.statista.com/statistics/249129/us-state-and-loca...

Kind of. The ethanol that's put into the gasoline is derived from corn, which is heavily subsidized in America.

consider the expansion of plug in hybrids, similar to the Volt, Clarity, Prius, and Kona, all extend the viability of the petrol engine. In many cases it moves into the roll of a range extender because its weight combined with fuel is drastically less than what battery technology can accomplish; an example is the Model 3 which has nearly 1100 lbs of batteries for 310 miles.

engines directly? variable valve timing will be common place and variable compression has debuted. more forced air systems and better injection tuning all present themselves. there is even ongoing work on two strokes and some of them are delivering better performance and emissions than four strokes.

Without abandoning piston engines entirely and going to turbines or something, modern auto engines are approaching maximum practical thermal efficiency for the conditions under which they must operate (being primarily horsepower-oriented rather than torque-oriented). You can get maybe 50% better if you're powering an oil tanker rather than a car, but you're not powering an oil tanker, but rather something that has to accelerate and decelerate and idle in unpredictable ways.

Hybrid was the last big improvement. Barring a radical new technology (and variable valve timing ain't radical), we might squeeze, what, 10% better thermal performance out? Get 40mpg rather than 37? Big deal.

And really, this is all driven by energy costs in the end. We're already hitting a point where commodity solar/wind electricity is cheaper than commodity coal, and much cheaper than commodity gasoline. This creates a tremendous market incentive for purely electric vehicles. And that tech has much more room for improvement than any gas engine - batteries will keep getting cheaper and more efficient for some time to come.

When my options are a $25,000 Ford or a $90,000 Tesla, an electric car seems like a dream. But when it turns into a $25,000 Ford or a $30,000 all-electric car (maybe from Ford!)... TCO starts becoming a very attractive argument, on top of the feel-good factor.

"This creates a tremendous market incentive for purely electric vehicles."

Can confirm. I bought a used Nissan Leaf two months ago from a dealer (being used it was a small fraction of the $25k Ford). A near-identical car (trim/mileage/colour) is now listed on their site for close to 30% more than I paid.

If we were living in normal times this would make no sense - but the TCO picture is changing that rapidly (owing to oil prices going up and used EVs being so scarce).

I paid $5k for my 2011 Leaf with 10 bars and 30k miles. Best decision ever. Seems like people are catching on though since theyre getting hard to find anywhere near that now.

Well.. these people you speak of can find their own.

Something something cold dead hands, etc.

We still have to see how HPPI and turning off two cylinders out of four at low speed improves fuel consumption. There are also alternative fuel options for ICE vehicles such as LPG for petrol powered vehicles and DME for diesel vehicles. Current diesels already do 65 mpg which is a big deal compared to 36 mpg. DME can be produced locally out of syngas from industrial processes or biomass.

Regardless, an all-electric car is going to be pushing 90% thermal efficiency - transforming energy into acceleration. A combustion car isn't going to break 40%. Exotic tech like variable timing and taking cylinders out of service isn't going to get huge gains - they're actually a lot of work for tiny gains, because all the huge gains have already been had. Moreover, electric cars will get that efficiency with no compromise in performance, unlike combustion cars with tiny, weak, "fuel efficient" motors. A Tesla Model S is the fastest car in its class, as well as the most efficient.

The only big win for combustion-based cars is the range potential, because the energy storage of liquid fuels is so much denser. I don't expect to see electric commercial aircraft in my lifetime. But biomass-based liquid fuel? Sure. It just won't be cost-competitive with solar/wind into a battery. It'll be limited to specialized applications where power/weight matters.

That's simplified as an engine + exhaust system + gas tank + gas + transmission weighs hundreds of pounds more than an electric cars engine alone. Electric cars do weigh more, but the difference is not that massive.

You can actually drive further using gasoline to turn a gas turbine > electricity > electric cars battery than using that same fuel to operate a normal IC car. But, nobody does that because wind/solar/coal/nuclear are all far cheaper than gas.

Plug in hybrids are probably only viable for a particular range of battery costs. When batteries are expensive it’s worthwhile reducing that cost by spending the extra money on a duplicated drive-train. As the cost of the battery falls the savings by having the extra drivetrain complexity fall.