When and why should I tune up
my car?

Most all of the American cars since 1981 are very sophisticated. On board computers control the timing and delivery of spark and fuel depending on the conditions (uphill or downhill, cold or hot). Many '88 through '92 cars owners manuals recommend the plugs be replaced at 30,000 mile intervals. I believe sooner is better. I change the plugs in my own cars every 20,000 to 25,000 miles. Statistics show that the loss of one mile per gallon over a years period of time will equal between $80 and $150. So, again, we are back to, "you can pay me now...."

Take a car that gets 19 mpg and travels 15,000 miles a year. At 19 mpg the car will use 790 gallons of gas at $2.50 a gallon which will equal $1975 in annual fuel costs. At 18 mpg it’ll need 833 gallons which will cost $2083. So that one mile per gallon loss will cost you $108 a year.

A single misfiring spark plug will affect the gas mileage much more than just one mile per gallon. A four cylinder engine with one misfiring spark plug stands to lose up to 25% of it's available power. At 60 miles per hour most engines are running about 2200 rpm. That's 36 revolutions a second. That's 18 times each second that each spark plug is firing. Over a period of one hour at 60 mph, each plug will fire 64,800 times.

If you own a newer car with a distributorless ignition system, take the above figure of 64,800 and times it by 2 which would equal 129,600 times an hour your spark plugs are firing, at 60 miles per hour.

If spark plugs in your car fire over a million times a week, doesn't a $125 to $250 tune up (depending on plugs, filters, wires, etc) once a year sound like a good investment?

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