Biggest Auto Maintenance Myths
What is a myth and how does it apply to automotive maintenance? Amythis defined as a legend, or historical story, that may or may not be based in fact. With the automobile having passed the century mark some years ago, and with its lineage having some connection to the horse and buggy (and horse traders) legends now abound. What made sense during the first 50 years is no longer appropriate.
A good example is the3,000 mile oil change. Many people still abide by this advice, except the auto manufacturers. Many modern cars inform the operator when an oil change is called for. Some systems actually monitor the oil’s condition; others determine oil condition based upon an algorithm developed over years that consider the type of driving and mileage on the oil etc. An oil change at 7,500 or more miles is not uncommon. Changing oil early will not harm an engine, but it is a waste of money and resources.
While on the topic of engine oil myths, another one is to never use synthetic oil when breaking in a new or rebuilt engine because it will prevent the engine from wearing in. In fact, much of the “engine break-in procedure” is comprised of a series of myths. First of all, many new engines come from the manufacturer with synthetic oil installed. TheCorvette engine, for example, is delivered with 5W-30 synthetic oil from the factory.
The engine break-in myth covers the gamut from “drive it like you stole it” to never exceed 50 mph for the first 1,000 miles. People have also recommended making the first oil change as early as the first 100 miles. The critical items to break in are: seating the piston rings to the cylinder walls, mating the camshaft lobes and valve lifters and seat the main and rod bearings.
Years ago the machining process forming the cylinder walls was not as precise as it is today and the cylinder surface finish was not as good either. Combustion pressure will seat the piston rings to the cylinder walls sorunning the engine hardis actually good for proper piston ring seating. Long periods of idle or low load can hinder this process and actually glaze the cylinder walls causing increased oil consumption for the life of the engine. The same is true of the other break-in components. Don’t drag race the engine, but don’t baby it and don’t run at steady speed for long periods for the first 500 or 1,000 miles. The first oil change should be at 1,000 miles on a new engine. This will remove the resulting debris from break-in and prepare the engine for getting on a normal oil change schedule.
Another popular myth relates to fuel grade. The myth is that using a higher grade of fuel will deliver more performance and better fuel mileage. Fuel grade requirement is determined by engine compression ratio and ignition advance. High compression engines require higher octane rated fuel to prevent detonation and knock. Most high performance vehicles use higher compression and require premium fuel. Premium fuels are blended to burn slower and prevent destructive knock. Lower compression engines do not require premium fuels because there is no danger of detonation or knock. Using premium fuel in a low compression engine will not harm the engine, nor will it offer improved power and performance. It will simply be a waste of the owner’s money.
Another point is of value while discussing fuels. Engines that are equipped with knock sensing will detect knock and retard ignition timing to prevent damage. If the owner attempts to save money by buying low octane fuel for his high compression engine, the knock sensor will retard the ignition and this will reduce performance and fuel mileage. Bottom line: use the fuel grade recommended by the manufacturer.
Very significant strides have been made in engine materials and lubricants. The general assumption was that a car with 75K to 100K miles was “used up”. It used to be that if a mechanic removed the cylinder head from an engine he would see evidence of significant wear. The top piston ring, a compression ring, would wear the cylinder material. Since the compression ring came with about one eighth of an inch to the engine block deck, where the cylinder head was fastened, the cylinder material would be worn away up to that point. That would leave a ridge of material at the top of the cylinder bore.
Recent inspection of a General Motors eight cylinder engine with in excess of 170K miles showed no such wear pattern. The “ridge” on this engine was carbon deposits, which could be easily removed with a putty knife. When reassembled this engine should be good for thousands more miles. If an engine is cared for properly, it would not be unreasonable to expect 250K miles and this blows the last myth to be discussed, into the weeds of ancient history.
