Dear Ole Mechanic;Engine Oil

I recently brought a newer used car because the old one was shot.  After I paid for it, I discovered that the original owner used Pennzoil in it.  My Dad would never use Pennzoil, because he said that it was paraffin-based oil and that the paraffin would break down too fast and the engine would wear out quicker. Is that true?  If so, what oil should I use? 

The car is a Ford Taurus with just over 30,000 miles on it.  The records in the glove box indicate that it had regular oil changes every 3,000 to 3,500 miles.

Shying away from Pennzoil


Dear Shying;

If there is any basis for this old wives tale about PennzoilŽ, I can't find any documentation for it.  Nor can I find any that would support the tales about ValvolineŽ or MobilŽ oils either.  If there were any problems with any engine oils, I suspect that they date back to the days before the API (American Petroleum Institute) was formed and started testing oils.  In the early days of engine lubricants, the consistency between batches of oil may not have been the best.  This would have been about 80 to 100 years ago.  Some time after that, as tetra-ethyl lead allowed higher horsepower ratings, the auto manufacturers started specifying things that the oil had to do to allow their engines to last longer.  How did they know what an engine oil would do?  The API started testing oils and certifying them if they would do what the auto makers needed them to do.  After an oil was found to meet the various tests, then the oil company got permission to put the API rating on the oil containersl.  Did the API reject any oil?  No, the oil companies were simply told which oils did not meet the requirements and what was needed to make the oils meet the minimun standards.  It may seem like a cozy arrangement, but it did make sure that there were quality oils on the market.

Were the auto makers, API and the oil companies always on top of their game?  No, as sometimes the car folks created a problem with new engine developments and then the oil folks had to play catch-up.  Overhead-valve camshaft failures in the 1956 and 57 Chevy’s comes to mind, as does the engine oil turning to tar in the  late 70’s and early 80’s Ford products.  The Chevy camshafts would wear out in less than 10,000 miles, and the Ford’s would cook the engine oil into tar in the oil pan.  An increase in oil film strength helped cure the Chevy problem, and better high-temperature resistance fixed the Ford problem.

I have covered this next part in a past article, but it is worth repeating.  There are two ratings printed on oil containers.  They are located in a double-circle logo.  The API rating is cited as two letters and the viscosity is stated in numbers--usually separated by the letter “W”.  The API rating starts with either an “S” for sparkplug-ignited engine oils or a “C” for compression-ignited diesel-engine oils.  Since I am not aware of any diesel powered Taurus’,s I will concentrate on the “S” rated oils.  The second letter indicates the level of testing.  An “SA” oil has met the lowest, easiest test.  The most stringent and demanding test is currently an “SL” or “SM” rating--it changes a lot here lately.  An API service rating of “SL” would work fine in your Taurus, but a rating of “SM” or higher will not hurt your engine in any way what-so-ever.  Any higher letter means that the oil has passed all of the easier tests below that letter.  For example, an “SL” rated oil will work fine in an engine that requires an “SH” rated oil, but a “SF” oil should not be used in it.  The viscosity or SAE (Society of Automotive Engineers) rating is the measure of how thick an oil is or how easy it pours out of the container.  An SAE rating of 30 says that the oil will act like 30 weight oil at freezing (32 degrees) and be rather  thick. It would also be like a 30 weight oil at hot temperatures (212 degrees) and be thinner.  A 10W-40 oil pours like a 10 weight oil at 32 degrees and like a 40 weight oil at 212 degrees.  No, the oil does not get thicker as it get hot--it just does not thin as much.

All oils must pass these tests to be able to put the API and SAE ratings on the container.  As a result, any popular brand of oil should work fine in your Taurus--even PennzoilŽ.  Because of the very tough tests that today’s oils go through, you could probably change brands of oil and not experience that other old wives tail--“Don’t change brands or your car will start burning oil!”  The one exception to that is do not change to a synthetic oil in an older, high mileage engine without keeping a very close eye on the oil level.  If it starts using the synthetic oil, go back to a regular oil.

What does the Ole Mechanic use?  My early 80’s pickup with 105,000 plus miles gets 20W-50 ValvolineŽ , my 2003 pickup with about 12,000 miles gets 5W-40 Mobil OneŽ synthetic, and my early 90’s car which has 130,000 plus miles and a lovely female name gets 10W-40 PennzoilŽ. Dear Daisy, despite her mileage and PennzoilŽ, still gets between 28 and 30 miles per gallon at 70 MPH.  Based on that, PennzoilŽ will work fine in your Taurus.  No, Daisy is not for sale.

Herr Professor Nuzanbolts