As befits one of the most vital parts of your vehicle's engine, your spark plugs require replacement every 24 months or 30,000 miles to maintain optimal fuel economy and engine performance. You can save some money by doing it yourself.

The interval varies depending on your vehicle's make and model. A vehicle equipped with the newer platinum-tipped spark plugs can go as far as 100,000 miles before plugs require replacement. Replacing your own spark plugs is relatively easy, as you'll see from the instructions listed below.

The first thing you'll want to do is gather all the tools you'll need. Of course, you'll start with a set of new spark plugs. Add a 3/8" drive spark plug socket, extension and ratchet driver, a spark plug gap gauge, and a brush or rag and set aside some time.

Now we're all ready to gap your spark plugs. Correct spark plug gaps can be found on the engine specifications decal underneath the hood. It's a good practice to stick with the brand of plugs originally installed in your car at the factory. For Ford products they are Motorcraft, in General Motors products they are AC Delco; Chrysler products use Champion. Refer to a parts guide to find the correct spark plugs, or ask the salesperson in your local auto parts store.

Okay, let's get to work.

Never change your spark plugs without the engine being cold. Wait two hours after driving to let it cool off. Grasp the plug wire by the boot, give the wire a twist and cautiously pull the spark plug wire out of the end of the spark plug. Don't pull the wires themselves or you may damage them. TIP: changing the plugs one helps avoid mixing up the spark plug wires.

Use either a bicycle tire pump or an air compressor and pump a few bursts of air to rid the spark plug area of dirt, dust or gravel. Alternatively, clean off the old plug and the area around it with a rag or small brush. These steps help prevent any foreign material from falling down into the cylinder when the plug is removed.

Remove the plug by turning it counterclockwise with a spark plug socket and ratchet. Spark plug sockets have rubber linings that prevent damaging the plug's ceramic case. Crack it loose, spin it out until it's off the threads, and take it out by hand.

OK, time to set the gap of the new plug with a spark plug gap gauge (Remember the proper gap is specified on the engine specs decal underside of the hood). You can buy a gap gauge at your auto parts store. Slide the correct thickness wire or feeler between the inner and outer electrodes at the tip of the plug. The feeler will slide between the electrodes with a slight drag when the plugs are properly gapped. If the gap isn't right, slightly bend the outer electrode until you achieve the right gap. Ensure the outer electrode is inline over the inner electrode.

Next, have a look at the cylinder head threads. Are they in good condition, clean, and free of dirt? New spark plug should freely screw into the cylinder head by hand. Any binding of the plug is an indication of debris or damage in the thread. TIP: lube the plug threads with a little grease or spray lubricant before you install them, this will make for an easier removal at your next spark plug change.

Insert the new plug into the spark plug hole by hand and turn it clockwise until it's snug. After finger tightening the plug, firmly torque it with your spark plug wrench/socket. Be careful not to over-tighten the plugs.

Reattach the correct plug wire to the new plug with a twist on the boot until it's firmly seated on top of the plug. You should feel and hear a click as the wire positively clamps onto the spark plug.

Repeat all the steps for the other plugs. Even taking your time this job will probably take you less than an hour. And that's it for another two years or 30,000 miles!

David Demetre is an author and the webmaster at http://www.Carrom.us, a premier source of Custom Car Floor Mats