How to Save Fuel by Adjusting Your Car's Idle Engine RPM

We have an old family car. Problems appear everywhere from the engine, the air-conditioning, chassis, exhaust, to the clutch and so on. And with an old car, the fuel efficiency isn't at its best. I was actually thinking of doing heavy mechanical service to improve my car's mileage, such as engine overhauling and installing aftermarket parts that may be a tad too expensive. However, I recently proved that a few simple turns of your flathead screwdriver can really save you a lot of money.

Almost a month ago, we had some serious car troubles. I was driving along with my family when the engine idle RPM (revolutions per minute) suddenly went erratic and then it steadily went up over 2500 RPMs even without me stepping on the gas. I immediately knew that there was a problem with the carburetor. The normal idling of my car before it happened was at around 1300 RPMs. We set it at that rate because we also have a problem with our compressor. If we turn the air-conditioning on, the engine idle goes down a bit so we kept it high enough so that the engine won't die down frequently.

I had the carburetor choked because they said that it was clogged or something and it was fixed. Now, the mechanic told me that the engine idling should be just around 800 RPMs so he set it to that rate. After a few days, I noticed that I did not have to refuel as often as I did before and I computed my car's mileage and was astounded at the results.

Before the carburetor problem, my car was running at about 5 kilometers per liter which is quite inefficient in today's standard. However, after we set the idle speed to 800 RPMs, I was shocked to see that my car is now running 8 kilometers per liter. That's a huge improvement. That's near double the fuel efficiency.

Come to think of it, if the engine idle is high, it consumes more gas even if you're stuck in traffic or if your car is just stationary while the engine is on. I then instantly thought that I should have set it to 800 RPM before. I don't usually drive my car to far places but I'm in the capital and heavy traffic is everywhere.

It actually depends on your car, but for carburetors, all you have to do is locate the screw to adjust the engine idling. Keep the engine running then turn it counterclockwise to lower the idling or clockwise to increase it. It may be the other way around depending on your car. Continue adjusting the screw a quarter of a revolution at a time until you get the desired idling RPM. As for fuel injected cars, you need to refer to your manufacturer or your manual since it usually has to be adjusted through the computer chip or the ECU (Engine Control Unit).

This simple step may improve your car's fuel efficiency however, just be reminded that results may differ for different cars which means that if it greatly improved my car's mileage, it doesn't necessarily mean your car will achieve the same relative improvement. But then, you can always try.

Sources:
Mechanics at Dallas Service Center
Quezon City, Philippines

Wikipedia - Fuel Injection
http://en.wikipedia.org/wiki/Fuel_injection