Magazine for the auto service professional
Issue link: http://asp.epubxp.com/i/684411
38 | ASP June 2016 Technical providing a super-slick flm to reduce friction. Again, the decision on which type of oil to use is often based on what the automaker recom- mends. One potential downside to using a full synthetic involves older engine designs where clearances and seal designs are not appropri- ate. For instance, an older engine design that uses a two-piece rear main seal is likely not a good candidate for a full synthetic. Full synthetic oils, by and large, provide a greater propensity for external leakage. In short, if there's a way to get out, a full synthetic will probably fnd it. Te engine sealing design must be extremely efcient in order to handle a full synthetic. Tat's why a full synthetic is not a good choice for vintage/collector cars such as those made in the 1960s and '70s muscle car era. A quality full synthetic can do an outstanding job of lubricating, but it poses a greater potential for leakage. Regardless of the specifc type of oil selected, the subject of oil change intervals seems to be a constant topic of discussion. Again, following manufacturer recommenda- tions is always the "safe" position. With that said, some automakers recommend extended intervals of perhaps 10,000 to 20,000 miles and possibly beyond. While these long-dura- tion oil change recommendations may appeal to some customers from a budget standpoint, technicians often vary in their opinions. If you can convince customers to have their engine oil and flter changed on a more regular basis, this can only beneft them in the long run. Some customers might rather spend a little more money by purchasing oil and flters on a more frequent basis simply in an efort to keep the engine clean, reducing the chances of sludge buildup and to keep oil passages clean and free-fowing. Tose who are more concerned with engine care may not mind spending a small amount of money more frequently in order to protect bearings and all frictional surfaces. Especially with a diesel engine, where contaminants are more easily deposited in the lubrication system, it may simply makes sense to "spend a little now to avoid spending a lot down the road." Te trend for automakers to feature smaller displacement engines (in an efort to improve fuel economy) has led to the use of direct- injection (GDI: gasoline direct injection), higher compression ratios and the increased use of forced induction such as turbocharg- ers in order to obtain desired performance. As a result of increased compression and turbocharger use, engine oils that are able to withstand higher operating temperatures in order to minimize coking and combustion chamber deposits and to maintain a constant and critical fow to turbochargers have been developed. An example is GM's recently specifed dexos1. We'll see more of these oil require- ments mandated by automakers, so it's more important than ever to be aware of an engine's oil specifcation. Oil flters All engine oil flters are not created equal. Te old adage "you get what you pay for" defnitely applies. Bargain-basement flters may not provide efcient fltration, or may create a pressure issue. In the case of an engine that operates on a higher pressure (let's say in the 50 psi or higher range), a cheap The worn-out, heat-cooked oil in this engine turned to a pasty, gummy, gritty goo that simply ofered no hydraulic flm support. The simple and inexpensive task of changing the oil on a regular basis would have avoided the issue. Oil sludge and resulting starvation resulted in a broken overhead cam in this example, where the cam simply could not withstand the stresses imposed by a lack of fowable oil.