CarTalk.com Best of Deals Car Reviews Repair Shops Cars A-Z Radio Show

Saving Gas

During the last gas price crisis, GM modified some of its big V8’s to run on 6 cylinders. Those were not perfect, but they worked. Could that be done today as an after-market modification to relieve the bite for people who are stuck with gas guzzlers?

If you’re referring to the infamous Cadillac V-8-6-4, I can tell you from personal experience that this concept did not work well at all. The limo that I drove required a warm-up time of at least 30 minutes, even in the summer, in order for it to be driveable. And, when it was necessary to accelerate quickly, I never knew whether I would get the power of 8 cylinders, or 6 cylinders, or 4 cylinders, leading to a driving style that was…leisurely… to say the least. It was just not possible to drive that car with any confidence, due to the unreliability of that old cylinder shut-down technology.

The technology that manufacturers are now using to shut down some cylinders is vastly superior to the technology of that old engine but this new technology is not something that could be readily added to an old engine. If cost is no object, of course it could be done. However, the cost of this type of retro-fit would be so high that any saving on fuel costs would be far exceeded by the cost of the equipment and the labor necessary to install it.

No. The ECM will do nuts if you try to disable any of the cylinders. Some newer cars and truck have ECMs programmed to shut off some cylinders to save fuel, like the Dodge Hemi models from 2001-on. But to do it yourself on a car not programmed for it will just cause more problems than you think.

No one liked the results. The fuel saved was minimal at best, reliability was a problem and derivability was less than ideal.

It would be far cheaper to just trade in your car for a more economical car than to make this modification, however, until that time, you do have the option of using zero cylinders during those times when the situation demands zero horsepower. Waiting for long trains to go by, waiting for your turn at the car wash, drive through teller, etc, and at intersections with really long light cycles. Don’t underestimate the idle fuel consumption of a big V-8 gasoline engine. It’s around .6 to .8 gallons per hour.

The easiest and cheapest thing to modify is your driving habits and your driving habits can make a huge difference in your urban gas mileage.

It was called the 8-6-4 system…and it did NOT work. In fact one dealership I knew of…disabled that feature when ever someone came in for service. It was one of GM’s hugh blunders.

And GM has a new system out right now that does pretty much the same thing. Although I hope they learned their lesson and actually designed it correctly and tested it thoroughly before they put it into production.

A number of cars do that today, from GM, Chrysler, and Honda, and they seem to save 1-2 mpg. Doing it after-market would be big $$$, because you not only have to stop the fuel injection, you have to stop the valves from opening. Definitely not worth the trouble.

I think an engine swap would make more sense, unless you’re Red Green.

There is no after market kit for this, but the automakers are all doing it again, only these days the electronics manage things much better.

There is no way to ease the “bite” for those who chose to purchase gas guzzlers. There have been alternatives to such vehicles all along.

I think that Red is more likely to try and run his vehicles on wood.