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No Automatic Benefit in a Neutral Stop

September 01, 1988|RALPH VARTABEDIAN | Times Staff Writer

Question: Is there any advantage to placing the automatic transmission in neutral while waiting at a stop light? I have for many years done this, especially when the air conditioning is on. I have always had the strong feeling that a neutral setting is easier on the engine while the car is standing still. But my friends say this is hogwash.--G.S.

Answer: This question comes up from time to time. Instinctively, many motorists feel that the engine and transmission are subject to additional stress while the car is stopped and the transmission is engaged. This is not the case.

If a car is stopped and the transmission is engaged, the transmission is under very little stress. The torque converter, which is a fluid clutch, disengages the engine from the transmission when the car is stopped. Thus, the various shafts and gears in the transmission are at rest. The hydraulic system is getting a full flow of cool oil as well.

As for the engine, it is under very little load while the transmission is engaged at a stop. The amount of fuel being supplied to the engine is usually the same regardless of whether the transmission is engaged or not. The engine idles somewhat slower and may seem to labor, but it is a comparatively very low load.

Because the function of an automatic transmission is to relieve the motorist of the manual chores of shifting, you are really defeating the entire purpose of the system. If you like to shift gears, maybe you should consider a manual transmission.

Q: Here's a question that has concerned me as an owner of a diesel car: What is the difference between motor oil that is certified for diesel motor use and that which is not? Will a diesel motor be damaged by oil not certified for a diesel?--H.F.S.

A: Diesel engines burn a heavy fuel that creates a great deal more dirt and soot than gasoline engines. To protect the internal part of a diesel engine, the oil needs more detergents and dispersants.

The additives must keep the piston rings clean from soot. Such contaminants increase engine wear and clog the oil control ring, causing major engine problems.

Motor oils suitable for diesel use are designated CC or CD on the oil container, an indication that they meet the standards set by the Society of Automotive Engineers. In addition, check with your automobile manufacturer to determine whether the new SG motor oil can be used in your diesel engine.

Q: I have a 1981 Honda station wagon with a 1,500-cubic-inch engine and automatic transmission. It's a wonderful car. It has two fans in front of the engine. But they never seem to come on. The temperature gauge on the dashboard is below normal. Is there a problem?--S.L.

A: You may not have any problem at all, especially since you don't have an overheating problem. The main electric fan is designed to turn on only when the coolant reaches a certain temperature, which on Hondas ranges from 185 to 200 degrees. The second fan runs only when the air conditioner compressor is operating.

Typically, the main fan seldom comes on while the car is cruising. The more likely case is for it to turn on while stuck in traffic on a hot day. You can easily check the system by turning on the air conditioner system and opening the hood to see if the fans are on. If they are, everything is probably working correctly.

If neither fan operates when the air conditioner compressor is on, you should have the system checked, because at least the air conditioner fan is not working properly. The main fan still could be operating correctly through a separate temperature switch.

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