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Synthetic Oil Benefits

Is synthetic motor oil really worth the extra money?  You can find people who will argue both ways; quite frequently with incredible passion.  It can be worse than the old "Tastes great - Less filling" argument!   I am certainly amused by the major motor oil producers that on one hand tout the superior qualities of their conventional motor oils and in almost the same breath advise that their synthetic offerings are the best thing since sliced bread.  My answer to the whole question is that the choice depends on a lot of things. 

From a pure upfront cost view, synthetic motor oil generally costs more than twice as much as conventional oil.  Right now (June 2013) the cheapest conventional 5W-30 (what P300K uses) at my local Auto Zone is 3.99/qt.  The Castrol Edge (they used to call it "Syntec" and I liked that name) that I have used since I bought the car is 7.99/qt (when you buy a 5.3 qt jug).  I feel very confident in changing the oil at 5000 mile intervals with the synthetic.  I could probably go a little longer but for me 5000 is enough.  I don't feel too good about going more than 5000 with conventional.  This is one of the first questions you have to ask - how long do you want to go between changes?  This is another area where you can get into all kinds of discussions.  Today's engines do run hotter (it's mostly for emissions) and they do rev higher (it's one way you get good horsepower out of small displacement engines).  One thing I know for sure is that when I take the oil out at 5000 miles it is black.  I don't have a fluid mechanics lab in my garage so I guess I can't check the viscosity or see how well the oil maintains a hydrodynamic wedge, but it looks used up to me.

As far as wear, I honestly believe that the cheapest conventional oil that meets the current SAE Standard of motor oil will do an adequate job of preventing wear and tear.  The question again is "is adequate good enough for you?"

Since I don't really consider synthetic oils vastly superior at preventing wear (although I do think they are superior), why would I even consider them?  How about improved fuel economy.  I have talked to a number of Subaru Forester owners that use both conventional and synthetic oil.  To a person they all report getting between 1-2 mpg better fuel economy when using synthetic oil.  This alone makes it worth it, especially with gasoline over 3 bucks a gallon.

I have tried synthetic oil in a number of different vehicles I have owned with widely varying results.  In my diesel equipped 2004 Silverado (Project C3500), I tried synthetic oil and over a 10,000 mile test period saw absolutely no change in fuel economy or performance (at least that I could note using my "butt dyno").  Considering that the C3500 uses 10 quarts of oil it just isn't worth it.  I also tried synthetic oil on my 1993 Chevy van equipped with a 350 again with no noticeable effect.  I used synthetic oil in my 2003 3.4 L equipped Firebird and got slightly better mileage.  I know that these were hardly scientific tests.  My feeling is that the smaller the engine the more impact the synthetic oil will have.  Again, that is based entirely on anecdotal evidence.

The bottom line on synthetic oil is that if you want to give it a try go for it. You can test it in the only vehicle that really matters - yours!  The fact is that I have a vehicle sitting in my garage with well over 200,000 miles on it that runs pretty well and still has plenty of power.  Would the case be the same if I had used conventional oil?  I'll never really know for sure since we didn't have a control car running conventional oil.

This page was last reviewed on May 17, 2014
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