Advised Not Because They Wear Out, But Rather as a Safety Factor Against Mistirings . Ever wonder why you should change the spark plugs in your car after every 10,000 miles. of driving? There's a good reason. The. 10,000-mile plug change rec- ommendation ts not actually based on the fact that spark - plugs are “worn out,” in the strictest sense, after 10,000 mile: 8, This figure—selected after extensive spark plug life tests — merely represents a safety factor beyond which plugs are likely to misfire under the sudden demands _. of peak acceleration or ex- tremely heavy load. It also represents the point at which gas economy begins to drop and starting becomes more dificult, Champion Spark Plug . Company engineers consider a spark plug worn out when it reaches the point where it is likely to misfire — regard- less of its appearance, And, contrary to popular opinion, misfiring doesn’t necessarily mean the plug falled to cre- ate a spark. It simply means that the plug failed to ignite the gasoline properly, wheth- er a spark was produced or not. Many Drivers Ask How can a spark be pro- duced and the plug stil] mis- fire? Because “spark track- ing” (or high-tension cur- rent leakage) through car- bon deposits on the spark plug’s firing end can result in a. wéek spark, which in turn causes incomplete burn- ing of the fuel mixture, and results In a loss of both pow- er and economy, High resistance, which de- velops as the spark plug elec- . trodes become ‘rough and uneven and the gap between the electrodes increases, also can result in the spark being too weak. Here, too, the gaso- line. isn't ignited properly and incomplete burning of the fuel charge can result. A new spark plug with the cotrect gap settling needs. about 5000 volts to fire. How- ever, as the plug remains in service, constant heat and chemical attack plus electri- eal erosion cause the gap to become wider, thus increas- ing the amount of yoltage to fire the plug. Spark plug gap growth oc- curs ‘at a rate of about .001 inch for each 1000 miles of driving. Consequently, a set of plugs that has been in service for 10,000 miles gen- erally will have gaps that are about .010 inch wider than, the original settings and higher voltage Is needed to make them spark. This is only for normal driving, : Operating the engine at very high speed can decrease the amount of coil voltage available to fire the spark plugs by 30 to 40 Percent. Ac- celerating to pass on a high- way may practically double the voltage burden on the spark plug. Slow Acceleration That's why misfirinig is first noticed while acceler- ating because it’s here that “the plugs actually can re-. quire more voltage to ‘pro- duce a epark: than ‘the igni- tion system. is capable of producing — especially if the plugs are badly worn... Now, back to the 10,000 miles ‘change - recommenda - tion. - Most spark plug. engineers agree that a safety factor is ‘needed in the spark plug to ensure proper plug perform- Freeways Cost Money But Yield Dividends Freeways may not be free, technically, but they are among the best investments the average citizen: makes ‘with his money,: According to the Highway . Users Federation for -Safety and Mobility, for every dol- - lar expended from the US. Highway Trust Fund on the Interstates system, about $2.00 is returned in direct users benefit. Taxes raiged from gasoline, , tires and trucks are building the most efficient and safe’ highway system the U.3. has ; ever enjoyed. _ This year the Highway Trust Fund {s ‘observing its- 15th Anniversary. Somé of.. -the highlights of the fund's benefits to the car owners‘are | listed below: @ The Federal-Aid Primary system accounts for leas than 30 percent of all U.S. roads but carries about half of all - motor vehicle travel. e The 42,500-mile Inter- state Highway system, to be ~— — in - compleied by: 1978, is nearly twice as cafe as other roads . and -streets. In recent years’ the fatality record on the In- teratate was 2.99 deaths per 100 million vehicle miles traveled ‘ve. 5,62 miles for - other roada, The Interstate system is saving 8,000 lives per year. . . @ In addition, the moneys paid into the Highway Trusl Fund by taxpayers provide “> indirectly a longer-lived car. _ Non-stop,-modern-designed — superhighways |help elimi. nate premature brake wear, prolonged idling time, less wear on suspension systems and shock absorbers among other-henefits. © Taxes, like death, may al- . “ways be with us but it’s good . ‘to know that some tax money - is being used as fruitfully as- - highway taxes. CLOGGED CLEANER A clogged air cleaner can help cause a 75 percent in- . . trease In hydrocarbon emis- slons from a car’s engine. _ FALL-WINTER, V7) Why ‘Change Spark Plugs at | 10,000 Miles’ Carbon Fouled Plug. ance under - every possible ce ‘operating condition. Conse- — . . quently, they try to'keep the © amount of voltage necessary. _ to spark the plugs well below. . the. amount of voltage that the coil ls capable of prodac- ing, And keep in mind, this . safety factor mnust take into consideration the fact . that : as the ignitidn system. be- . comes older, its potential. high voltage output drops off. A new ignition system, ‘tor example, may be able to-pro- — duce over 30,000 volts of elec- . tricity, The same system af- ; ter 20,000 or 30,000 miles.°- _ without replacing any. of ee. a parts may only be able to. . produce 15 to 20,000 volts.. —.-- No “IDLE” RUMOR... According te a University of Michigan ‘engineering school study, hydrocarbon. emission from an automobile -. engine Is reduced an average. ‘of 55% at idle after a tune- . up. . All Lines —— All Sizes. At Competitive Prices” LIKE AN AIRPLANE: TIRE WITH THE ‘STRENGTH OF 4-PLY DUPONT NYLON " B. F. Goodrich Silvertown 660 . Former original equipment tire, now with. the extra strength of 4-ply. DuPont Nylon—the same rugged cord used in tires for the big jets * High: mileage at a special low price « e ‘Full range of sizes e° | . Sjnitbancss P mmmmy TRUCK & CAR THR ~ VOLCANIZING: & RECAPPING A SPECIALTY — ps “LAST CHANCE a. THIS PRICE rors TIRES ONE LOW PRICE. ALL SIZES! aT THis Bancatn OnLy | ar ans KEITH AVE:, TERRACE, B. C. -CEDARLAND: TIRE. SERVICE _ a)