Making the best gas mileage cars is at the forefront of every auto manufacturer’s agenda these days. Big trucks and full sized SUVs languish on auto dealer’s lots throughout the country, as consumers look for something that will save them money on gas, rather than draining their 401k to fill their tank. Car manufacturers have responded as best they can but lead times on new vehicle models are measured in years, not months.

Developing and implementing new gas saving technologies and staying within the ever changing regulatory framework takes time, and there’s not much the manufacturers can do about it. Those of you thinking that the Big 3 passed on the 100-mpg carburetor because it was too expensive, or that it was suppressed by the oil companies should take this time to remove your cranium from which ever bodily orifice in which it’s buried.

General Motors alone employs over 6,000 power train engineers in an attempt to develop powerful, efficient, quiet and smooth engines and transmissions that consumers want to buy. You should ask yourself why:

A) None of these bright star engineers have stumbled on the formula for the esteemed, 100mpg carburetor?

B) GM has squandered hundreds of millions of dollars developing fuel delivery, engine management, and other technologies that deliver increased fuel mileage, reduced emissions, and smooth running engines if they could have just cut a deal to fast track the 100mpg carb?

C) The whole 100mpg carb idea just doesn’t pass the smell test. You’re not going to get 100mpg, good power, a smooth running engine, and low (actually almost non-existent these days) emissions by simply swapping a carburetor. Also consider that no carburetor equipped vehicles are manufactured by major auto manufacturers any longer, and haven’t been for about a decade. There’s a reason for that.

Since the 100mpg carb isn’t going to be around to increase the fuel economy of vehicles, let’s take a look at the new technologies that are being used to save you gas on your daily slog to work.

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Cylinder Deactivation – This is the technique of cutting off certain cylinders when the power isn’t needed. In many cases the valves are closed to reduce pumping losses. There are many different names for this; Chevy calls theirs Active Fuel Management™, Chrysler marketing gurus came up with Multi-Displacement Engine, and Honda likes Variable Cylinder Management™. This is a very nice way to use modern engine management systems to really manage the engine in a quest or better fuel efficiency. Depending on how you drive, you’ll save about 10% – 15% on your fuel bill over a comparably equipped vehicle without cylinder deactivation technology.

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Multi-Speed, electronically controlled automatic transmissions and Continuously Variable Transmissions (CVTs) – The advent of extremely sophisticated vehicle management systems have allowed electronic control of your vehicle’s transmission to the n’th degree. The greater amount of transmission control and coordination with the engine, coupled with the increased number of ratios offered by many transmissions (an infinite number, in the case of the CVT), allows large increases in gas mileage. As an example, the new 2009 Chevy Impala 4-cylinder went from an EPA 30mpg highway to 32mpg with the change from a 4-speed automatic transmission to a 6-speed unit.

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Turbocharged, small engines – Turbocharging technology coupled with smaller displacement engines has experienced a resurgence in the last couple of years. Acura for example has offered their first turbo engine, the turbo 4-cylinder found in the new Acura RDX small SUV (You’ve got to love a vehicle named after the explosive that’s the basis for the military plastic explosive C-4).

The increased capability of sensor and engine management, fuel delivery, and ignition systems, combined with better materials technology and improved combustion chamber designs, have breathed new life into the turbocharged engine. The added expense and weight of the turbo and its’ associated plumbing can’t really be justified when gas prices are low, but if they stay over $3.50 a gallon, expect to see the turbo / small engine combo stick around for a while.

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Engine cut off / restart – Your car never gets better mileage than when it’s not running (infinite mpg), and it never gets worse mileage than when it is running but not moving (0 mpg). Now, what’s good enough for your golf cart moves into the realm of automotive normalcy with the adoption of auto engine cutoff / restart technology.

Used by most hybrids, this changes your vehicle from living in the domain where it gets the absolute worst mileage to the one where it gets the absolute best. That change adds up to increased gas savings and better overall gas mileage with the improvement coming in city driving, the bane of most vehicle’s fuel economy profiles.

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Direct fuel injection – As I mentioned earlier, there hasn’t been a non-fuel injected car sold in the U.S. for about 10 years. Most cars now use port fuel injection, where fuel is injected into the intake port, right behind the intake valve. With direct injection, the fuel is injected directly into the cylinder using high pressure fuel injection systems. This gives three big advantages; The cooling effect of the fuel allows higher compression ratios for increased engine efficiency, more precise fuel timing and delivery is possible, and better fuel atomization is realized. These add up to an additional 10% – 15% in fuel economy, often coupled with better drivability and more power.

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Hybrid power train technology- You probably saw this one coming a mile away. With the Hybrid Prius’ popularity (even though I personally prefer the Honda Civic hybrid) of late it’s hard to Escape (hey, isn’t that another hybrid) the conclusion that combining both an internal combustion and electric power plant with some of the technologies mentioned above will lead to much improved fuel economy, especially in city driving. Looking at most manufacturer’s best gas mileage cars, it’s fairly obvious most of them are some variation of hybrid.

The hybrid’s ability to recapture heretofore lost energy through the use of regenerative braking, it’s ability to move at lower speeds purely on electric power and the ability to shut off the engine completely when stopped really deliver far better city gas mileage. Soon hybrids will be implemented with small, common rail diesel engines to deliver even greater fuel economy, possibly on the order of 60 – 70mpg in the city.

These are the technologies used to make the best gas mileage cars. There are certainly improvements coming as these technologies are refined. In addition several promising, new developments are on the way in the not too distant future that will make the best gas mileage cars in the next decade fairly embarrass even the best hybrids of today. In fact the vehicles that do burn fuel probably won’t burn gas at all, but some sort of biodiesel.

Until next time…….