Use caution with grease lines that run out of the machine frame, intended to provide easy lubrication access points. Because these line extensions often carry more than a few shots of grease, the grease entering the bearing will not be robust and fresh. Vibration, time and temperature changes can lead to leaching of critical oil components from the grease thickener, leaving a dry soap in the tube.

Without visual access to the bearing area, there can be numerous undetected problems. The best approach is to provide access to the lube point as close to the bearing as possible. This enables the bearing to be inspected and ensures that fresh grease enters the lube cavity. (William Morgan, Maintenance Engineer, Morgan & Associates)

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From the "Lubrication Excellence 2007 Conference Proceedings":

An excerpt from the paper "Automotive Oil Drain Frequencies".

Oil quality is a major factor in oil drain frequency. Using lubricants formulated with superior base oils, such as Group II and Group III and traditional synthetics, can extend oil life and thus oil drain intervals. If the oil drain interval is being dictated by contamination, such as soot or silica, then superior base oils may not provide any benefit. Premium additive packages with better antioxidants and detergents can have a huge effect on drain intervals. One major oil company feels that this is the key to extending drain intervals. Another major oil company is promoting gasoline passenger vehicle oil drains of 15,000 miles (25,000 km) by using premium base oils and additives.

Sump capacity is another major factor. A larger volume of oil in the sump, very simply, provides a larger quantity of oil additives to deal with the oxidation or soot created in the oil. In some cases, additional filtration devices are added to a piece of equipment (an engine) more for the purpose of increasing the oil volume than for improving the actual filtration capabilities.

More information about the "Lubrication Excellence 2007 Conference Proceedings".

"How does a Group III engine oil compare to a Group IV in its cleaning ability? I have read and understood the potential problems of switching a higher mileage engine from a conventional oil to a synthetic PAO but is there less inherent risk with switching to a Group III? From my understanding esters act more like a solvent (more aggressive I assume) and detergents, and dispersants more or less attach themselves to sludge and other contaminants and carry it away in that form."

Most engine oils are now formulated with Group II (hydrotreated) or a mixture of Group I (conventional mineral oil) and Group II base oils to meet the latest API gasoline (SM) and diesel (CJ-4) performance designations.

Because Group III and Group IV (PAO) base oils are both considered synthetics (since 1999), any oil labeled as a full synthetic, would contain either Group III or PAO, or both. Any oil labeled as a partial synthetic or semi synthetic or synthetic blend would contain Group I or Group II (mineral oil) plus some amount of Group III or PAO (synthetic).

There are no designations for us, as end-users, to know what specific base oils the oil formulator has used, so your question is a bit academic in nature. We would never know if we were purchasing a Group III engine oil vs. a Group IV (PAO) engine oil.

But, from an academic point of view, I would expect the cleaning ability of a Group III and a PAO to be similar (generally poor). Again, academically, I would expect less risk of seal issues etc. when switching from a Group III (as opposed to a Group I) to a PAO, as the Group III and PAO are chemically similar.

Ester synthetics have a higher degree of solvency than Group II, III or PAO base oils. This means they will dissolve additives and deposits more readily and may cause some seals to swell slightly (they also can remove some paints). These characteristics (not the paint removal) can be beneficial and some oil formulators will add some small amounts of ester base oils into their synthetic (Group III and PAO) formulations to improve these characteristics.

Bob Scott, Noria Corporation

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