JUST how good is the gasoline you put in your car? That's a question that's been nagging oil companies and automakers alike for more than a year. At issue is the problem of plugged fuel injectors, a condition with which many late-model car buyers are all too familiar. To remedy the situation, an increasing number of refiners now market high-detergency fuel, the purpose of which is to clean the injectors and keep them clean. Even so, high-detergency gasolines are only a quick fix. For the long term, the injectors themselves are being redesigned.
Fuel injectors started out in the throttle body, replacing the carburetor. But then the auto industry began to use port fuel injection - in which the fuel is sprayed directly into each engine cylinder - for increased performance and better fuel economy. Port fuel injection, much more simple than a carburetor, provides a lot more power.
``We were not aware that port fuel injection had special requirements in terms of detergency,'' explains Mr. Morgan.
The problem first surfaced more than two years ago when General Motors introduced its first large volume of cars with the new system. GM says that by the end of the 1980s, at least 90 percent of its vehicles will be fuel-injected.
To get at the plugged-fuel-injector problem, Howard H. Kehrl, vice-chairman of General Motors, wrote to the oil companies a year ago asking for better fuel for its port-injected cars.
The oil companies responded by either adding or increasing the detergents in their fuel. Now at least 16 gasoline brands, including many of the independents, are advertising gasolines with detergent properties suitable for port-injected engines.
``Detergency is needed to keep the intake system clean,'' reports Joseph Calucci, a General Motors fuels expert. He adds, ``with a blocked injector, you get bad throttle response and the car drives poorly.''
Yet some of the gasoline additives themselves may contribute to deposit buildups on other parts of the fuel-intake system, according to a study by the Chevron Research Company.
Some of the additives, the study reports, may actually contribute to valve and port deposits. As with injector deposits, intake valve and port deposits have an adverse impact on vehicle performance, including poor starting and warmup performance, loss of power, and increased emissions.
``Each time the technology changes,'' says Charles Morgan, a fuels expert at Mobil Oil Company, ``the requirements on the gasoline can change.''
The plugged-injector problem arose more than two years ago when the auto industry began the mass installation of ``port'' fuel injectors in their cars.
Mr. Calucci, head of the fuels and lubricants department at GM's Technical Center, says, ``We've worried about carburetor deposits for years, but they're easier to handle than port-fuel-injector deposits. The carburetor jet sizes are huge compared to the pinhole in the fuel injector.''
When the engine is shut off, the temperature goes up and deposits form. Both the fuel flow as well as the air flow keep the engine cooler when it's running. Also, the clogged-injector problem is worse when a car is driven on short trips. The long-distance driver rarely has a problem.
Some oil companies, such as Mobil, say that their premium unleaded fuel is designed to clean up clogged injectors, while regular unleaded will keep them clean. Shell asserts that either grade of its fuel will clean up clogged injectors.
Chevron claims that its patented Techroline keeps the entire fuel-intake system clean, including fuel injectors.
In any case, detergent fuel is only a quick fix. Automakers and their suppliers are pursuing design changes that would make future systems less sensitive to fuel quality.
Bosch of West Germany, which supplies 90 percent of the fuel-injector market worldwide, and other companies are redesigning the injectors. Allied-Signal, a major supplier, claims it's new DEKA high-performance injector ``is virtually immune to deposit buildup.''
Nearly a dozen major automakers worldwide are testing the new multipoint system, according to Allied-Signal.