Automotive Fleet

JAN 2014

Magazine for the car and truck fleet and leasing industry

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Page 49 of 67

MAINTENANCE The foundation for a preventive maintenance regimen has remained the oil change. with an exception for what was called "severe use" — generally much higher annual mileage — in response to which the interval was reduced to 3,000 miles. Fleet use, up to double or more than the annual mileage accumulated by the typical consumer, ft that "severe use" defnition, so the 3,000-mile oil change was a staple of the feet PM schedule. Time and technology began to change this beginning in the mid-1970s, with the introduction of the frst American Petroleum Institute (API)-qualifed synthetic motor oil, Mobil 1, and by the mid-1990s nearly every motor oil manufacturer featured synthetic products. Te primary advantage these synthetic products provide is the maintenance of viscosity, particularly in cold weather, but also resistance to breakdown due to heat, friction, and chemical contaminants. Tis led to changes in normal oil change intervals, lengthening them beyond the time-honored severe use 3,000 miles to 5,000 and more. But, not every feet made this change. Te price of synthetics was, and remains, higher than that of regular oil What has changed further is that cars and trucks are simply better made, with better materials, than they were in the past, and thus do not require oil and flter changes as ofen. Tus, the combination of synthetic oil products and higher quality engines has made oil and flter change intervals longer than ever before. Electronic Ignition: No More Tune-Ups Beyond oil and flter changes, another standard part of a regular preventive maintenance regimen was the "tune-up." 48 AUTOMOTIVE FLEET I JANUARY 2014 Prior to the advent of the electronic ignition, a tune-up was usually recommended at 12,000 miles (once each year for consumers, twice for feet use). Standard items in this process were: ● Ignition points (clean or replace). ● Spark plugs (clean/regap or replace). ● Condenser (replace). ● Distributor rotor (replace). ● Distributor cap (clean or replace). ● Ignition timing (check and set if necessary). ● Carburetor (adjust). A tune-up included the cleaning or replacement of ignition points and spark plugs. Tose old enough to remember the "points, plugs, condenser, and rotor" days of engine tune-ups know that it was an important PM activity. So, what has changed? Two primary technological advances — electronic ignition and fuel injection — have not only nearly eliminated the need for an engine tune-up, they have eliminated most of the items that tune-ups involved. Prior to electronic ignition, the fuel/air mixture was ignited by a mechanical ignition. Put very simply, plug wires ran to the distributor cap, under which was the rotor. As the rotor turned, each plug was fed the spark as the rotor contact hit the distributor contact. It worked, and worked well when in tune; however, it was subject to wear that required the tune-up. Te electronic ignition eliminated the need for the ignition points, rotor, and distributor cap, and the adjustments and replacements thereof. By 1975, the Detroit "Big Tree" (Chrysler, Ford, and General Motors) made electronic ignition standard on all models. Today, the fuel ignition portion of a tune-up (as well as the parts associated with it), at least as a standard item in the preventive maintenance schedule, is a thing of the past. For most of the life of the internal combustion engine (ICE), carburation provided the air fuel mixture needed to ignite in the engine cylinders, which, in turn, pro- vided the power that ran the engine. Again, to simplify a more complex device, the carburetor provides the mixture of air and gasoline that is needed in the cylinders, where it is ignited by a spark; the ensuing explosion moves the pistons, etc. Te mixture must be exact; if the mixture is too "lean" (too much air), the engine won't run, or will run weakly. If the mixture is too "rich" (too much gasoline), the engine will run roughly. Tune ups included the adjustment of the carburetor mixture, as well as the choke (which provided extra fuel for cold weather starting). Te last carbureted vehicle sold in the U.S. was in 1990, and, since then, vehicles are equipped with fuel injection, frst with "throttle body" fuel injection, followed by "multi-port" fuel injection. Fuel injection provides far more accurate fuel/air mixture calibration, and does not require regular adjustment. Te result is more complete and clean combustion and better fuel mileage. Covering Other PM Items Most PM schedules include other work, as well as various "checks" of systems. Here are some of these items that were checked, and whether they've changed over the years: Transmission. It was generally accepted that, once per year, feet vehicles should have the transmission fuid and flter screen changed. Transmissions create a great deal of heat via friction, and this heat (if it exceeds about 175 degrees Fahrenheit) can cause fuid to begin to oxidize, break down, and lose its lubricating properties. Changing the fuid and screen at about 30,000 miles has always been a standard item of preventive maintenance. Tere are, however, automatic transmission fuids (ATFs) which the manufacturers claim will last up to 150,000 miles. While this may be true, performing this PM once or twice in the life of a typical feet car is a great deal less expensive than an overhaul. Tis is as true today as it was decades ago.

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