Synthetic motor oil manufacturers (Amsoil in particular) recommend very long "drain intervals" for their products when used with quality oil filters. You may, for instance, change a synthetic oil one time in 20,000 miles (with one oil filter change along the way)while changing a petroleum based oil four to six times (assuming drain intervals from 3,000 to 5,000 miles). Hmm, this seems like a great way to save time and, according to my calculations, save money.
What does your automotive expert think about synthetic motor/transmission/gear oils? I do understand than one must stay w/in manufactures recommendations on oil changes for those vehicles still under warranty.
Jim and Mary
Jim and Mary,
Well, synthetic oils have come a long way since their inception. You may remember back when Mobil 1 was the only synthetic on the market. It was also said that you should NOT mix synths with petroleum based motor oils. Well those days probably have passed (like the days when you could not rotate your radial tires left to right). There are some oil manufacturers that are actually making a blend of petroleum and synths (Valvoline, I believe). As for their claims to the extended oil life, this is what I recommend:
The one benefit that I have seen for the synths is that when you are the responsible party in your family for taking care of the cars and your other half forgot to tell you that it was due to be changed 10,000 miles ago, then at least you have some protection. The synths generally have a longer life because they resist thermal breakdown or heat better than non synths...
My personal advice is to change the oil every 3000 miles (5000 at the absolute most)! The oil is your engine's life blood... keep it clean, and you will enhance its life and it will most likely give you a long service life. Now, if one has a turbo charged or a super charged engine, then I would reduce that number to 2500 miles.
As far as synth tranny fluids, there is a product out there that is synthetically made that replaces the whale oil that used to be in the fluid way back when (early '70) This additive increases the life of the tranny fluid. As far as other gear oils, well then they don't normally get changed that often. The differential oil is usually changed about every 50,000. One reason it lives so long is because there is no heat problem like in the engine oil. So a synth there may not justify the added expense. Eventually though, they will need to stop making oil from petroleum based products. But, that wont happen for a long while.
Bob, The Auto Answer Man
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