Posted: Jan 30 2011 at 3:38pm | IP Logged

I found this site (see below) and it graphically shows what happens if you use an SA (non-detergent) oil in a modern engine.  They compare it to SL oil but that has been supplanted y SM and now SN.  Keep in mind these SA oils are still for sale at discount house, Wal-Mart and convenience stores. DO NOT use these in any modern engine or equipment.

http://www.ilma.org/resources/impact_lowqualityoils.pdf

Posted: Jan 31 2011 at 10:58pm | IP Logged

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   In the old days the quality of all motor oil was sad. In 1953 I was changing oil and filter in my dads car every 1000 miles and doing it at the dealership I was working at. One day I tried to drain the oil and nothing drained out! The whole bottom of the pan was full of sluge except a quarter of an inch around the oil pickup screen. I also had a 1950 Cadilac  in the same condition.

   In the mid 1950's AMC V-8's had ring seating problems. To fix the problen we dropped the beakin oil at 500 miles then put Pennzoil Transport a non-detergent then at 1500 miles we installed Pennzoil with Z-7 (detergent). All customers with these test vehicles got exellent oil mileage after that. I have used a lot of Pennzoil since then with zero problems. Most of my mechanic friends say it's bad stuff.

Have a good one.. Don S..

Posted: Feb 01 2011 at 10:31am | IP Logged

There is still zinc and phosporous in motor oils for cars.  It is now set at 800 parts or less in SM and SN oils.  SL had, I believe, an allowed level of 1200 as did older oils like SJ.  It is really academic for most modern engines as very few engines any more have rocker arms run with high lobe cams and solid or flat bottom hydraulic lifters where contact pressures are VERY high.  However, if you "cam" an engine and put strong valve springs in, you need to break it in with lots of zinc and phosphorous to prevent failure and you need to run an SL oil.

The compound used is a zinc thiophosphate.  It can volatilize and eventually kill a converter which is why it has been reduced.  They are now using a newer form of the chemical that is also less volatile.  With overhead cams, the pressure on cam lobes has been greatly reduced so all of this works together in the modern SM and new SN oils.  This is also true for roller lifters.

In motorcycles like a Harley, you can still have the need for the higher level of adds.  You really need to follow the manufacturer's recommendation for an engine.  In my lawn mowers etc that still call for a stright 30 wt, I buy Rotella 30weight which now only has diesel specs.  It used to carry the SJ rating but since that is obsolete and not supported, they removed it.  But it has the higher levels of phosphorous and zinc.