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Old 01-17-2015, 01:08 PM   #1
DF Sales&Marketing
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Join Date: Apr 2007
Member Number: 207
Posts: 268
Default Refresher on Engine Oil Requirements

An updated re-print from October 2008 by request

years ago, an automotive supply store or shop could consider its shelves well-stocked if it contained a selection of single-viscosity oils in detergent or non-detergent blends. Today, they are confronted with stocking a variety of multi-viscosity oils, including 0w-20, 0w40, 5w20, 10w30, 15w40 and 20w50, not to mention stocking some of these viscosities in synthetic and non-synthetic bases.
Although the number of oil viscosities currently available is bewildering, it’s also important to remember that the most important factor in selecting motor oil for specific applications is the quality of the oil’s base stock and its particular blend of additives.
With that in mind, it’s also important to remember that motor oil must efficiently perform at least six different jobs in the engine’s crankcase. It must, for example:
reduce friction between moving parts.
Seal piston rings against the cylinder wall.
Cool pistons and engine bearings.
Cushion bearings against shock loading.
Clean sludge and varnish from engine parts.
Prevent corrosion while an engine is parked or in storage.
In addition, application-specific oils might, for example, be formulated to prevent piston rings from sticking or the camshaft from scuffing in particular applications.

Modern engine lubrication
before we begin to understand the need for so many different engine oils, it’s necessary to understand the lubrication requirements of modern engine design. The primary difference between a modern engine and one of two or three decades ago are greatly reduced oil clearances in bearings, pistons and piston rings, more precise machining and higher power output per liter of displacement.
Because modern engines depend upon three-way catalytic converters to reduce exhaust emissions, it’s particularly important to prevent oil, oil ash and oil additives from entering the exhaust stream and contaminating the converter.
To reduce oil consumption, engine manufacturers have greatly reduced piston, crankshaft and valve guide clearances. They’ve done this, for example, by using hypereutectic materials in some piston designs; precision boring and honing of cylinder walls; micro-polishing of crankshaft journals; and using more durable materials in valve guides and valve guide seals.
In all cases, oil viscosities have been reduced to flow through tighter engine clearances during start-up and cold-engine operation. Other, less visible issues also affect how oil is formulated. Engines with hydraulic lifters, hydraulic timing chain tensioners, and variable camshaft timing, for example, require anti-foaming agents to prevent the oil from retaining air bubbles that reduce the efficiency of these mechanisms.
Because overall volumetric efficiency has been vastly improved during the past several decades, engines are designed to operate at crankshaft speeds and bearing loads unheard of a decade ago. Unfortunately, many of the additives used a decade ago to increase the load-bearing, anti-scuff and anti-shearing capabilities of conventional motor oils have been reduced or eliminated from oil formulations to prevent damage to the catalytic converter.
In addition, the oil change intervals of modern engines have doubled or even tripled in length [according to the newer owner’s manuals - this due to heavy government intervention], so modern oil is required to have a longer lasting additive package than ever before [which isn’t necessarily true, folks!]. Without adequate additives, conventional oils tend to oxidize and lose their detergency long before the oil change interval expires [a very true fact]. The result is the oil gelling from oxidation or a heavy coating of sludge being deposited in the valve train and crankcase areas.

Refresher notes on what the api ratings are for

since there have been so many changes lately in the engine oil rating system, here is a good reminder on how to read what the American petroleum industry’s (api’s) symbols represent.
First of all, engine oil specifications are broken down into two categories, one for diesel, which is the letter “c,” which stands for “compression.” the other for gasoline which is the letter “s,” which stands for “spark ignited.”
when you see these letters on an oil container, it tells you what class the oil was designed to be used in.
Secondly, the letters after the “c” or the “s” represent the oil grade level; for example, the letters “sa” would indicate that it is for gasoline engines and the “a” in that group would be the very first rating which was given to engine oil at the beginning of the program…..incidentally, don’t ever use that in a newer engine as it does not meet newer engine needs and can actually be damaging, it has been ruled obsolete. But to get on with it, the next oil grade level would be “sb”, then “sc” and so on up to the current and newest gasoline specification, “sn.”

diesel specifications also began with the letter “a” after the “c” designation, and progressed in the same manner as the gasoline mentioned above. The latest diesel designation is “cj-4.” the number “4” after the “j” denotes that it was designed for 4-stroke diesel engines. What does this all mean? All of the new engine oil designations are said to be “backward compatible” in other words, they can be used in any of the previous designations, such as in the case that “sn/sm” can be used in gasoline engines requiring “sl”, and earlier, and “cj-4” oils can be used in diesel engines requiring “ci-4” and earlier.
However, and here is the confusing issue, since both the gasoline “sm” and the diesel “cj-4” went into effect late in 2006 to meet the newest epa requirement for low emissions, their additive package, especially for the protection against friction and wear have been reduced substantially.
Most engines made for service with the low emissions systems must use the “sn/sm” or cj-4” oils to be compliant and for protection of their emission systems. These are the oils which are commonly available now on the shelves, or from the oil jobbers.
Pre-2007 engines, both gas and diesel will benefit more from oils which have the previous api rating of “sl” or “ci-4, ci-4plus” oils. Oils which have the letters ““sn/sm” or cj-4” along with meeting “sl/ci-4” will contain the lower additive package. “sn/sm” grade oils will not give the protection needed for older gas engines, especially those using flat-tappet cams.
The choice is yours
because of the concern for premature wear in pre 2007 engines, a handful of engine oil blenders have continued to make the “sl” and “ci-4” designations. Some of these are very hard to get and more than likely most of which will be phased out after a period of time.
Swepco engine oils will continue to be available in both the gasoline and diesel service ratings, and these products’ formulations will contain the higher levels of phosphorous, zinc and calcium than the “sn/sm/cj-4”oils, however should not be used in engines requiring “sn/sm/cj-4.”

the following list will denote the api grade rating and the proper oil from which to choose with swepco engine oils:
· 308– 5w40, 15w40 meets sn/cj-4
· 303– 5w20, 5w30, 10w30 sn/sm
· 306–10w30, 15w40, 20w50 sl/ci-4
· 305– sae 40wt meets ci-4
please note: all of these products are deemed “backwards compatible” and are approved by the api to be used in previous grade ratings.

Important note: swepco 305 and 306 engine oils contain a higher percentage of phosphorous, zinc and calcium than most other engine oils did which were rated “sl/ci-4” (before the change to “sm/cj-4). They offered more protection then, as they continue to do now, for the demanding applications our customers have — you can rely on the experience of over 80 years in the industry.
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