Amsoil oils--first introduced in the 1970s--were one of the first synthetic formulas to appear on the market. Synthetics are designed to improve engine performance and extend engine life. Longer intervals between oil changes is another added benefit; however, potential problems can develop depending on the number of miles on the car and whether or not someone is switching to Amsoil or has used it all along.
Regularly scheduled oil changes are one the most important maintenance requirements for prolonging the life of a car engine. A car that uses the standard, petroleum-based oil grade typically requires a flush and fill every 3,000 miles. A car that uses Amsoil--a synthetic oil--can go as long as 25,000 miles before the next scheduled oil change. Since the 1980s, many car manufacturers have designed engines to use synthetic oil products, so if Amsoil has been used throughout the life of the car, few problems may result from its ongoing use.
Switching from a standard, petroleum-based oil to an Amsoil synthetic formula is where problems can develop, especially with cars that have 30,000 miles or more, according to Pecuniary Inc., an independent product review site. Part of the problem has to do with the high-detergent agents contained in the Amsoil formula. And while petroleum-based oils also work to keep engine components clean, they're more likely to coagulate and clog up engine parts and seals over time.
After switching from a pertroleum-based oil to Amsoil, some cars may begin to consume oil, meaning you will have to add oil more often than usual during routine checks. What happens here is Amsoil's enhanced cleaning agents are cleaning out residues and sludge left over from the previous oil, according to Pecuniary Inc. As a result, the oil filter is catching more sediment, sludge and varnish than it was designed to handle. When this happens, the filter's bypass valve begins to malfunction causing unfiltered oil to circulate through the engine. In effect, contaminants build up inside engine components, which cause excessive oil use and consumption. In this case, changing the oil filter on a more frequent basis may be necessary until sediment build up has worked its way through the system.
Another possible problem car owners can run into when switching to Amsoil synthetic oil is possible leaky or cracked seals. In general, the more miles a car has the more worn its engine seals become. Switching to a heavy cleaning agent like Amsoil can cause leaks to appear once sediment build-up is cleared away, according to Pecuniary Inc. Eventually, leaks may go away once seals re-swell and fill in the new gaps. In the case of valve seals, leaks may be a sign that cracks have formed as a result of over-drying. In effect, previous sediment deposits worked to fill in valve seal cracks. In this case, valve seals may eventually have to be replaced depending on "what's left of them" once Amsoil has worked its way through the system.