The drive for greater fuel efficiency and lower emissions isnt just a concern for automakers. It also affects original equipment manufacturers of large, high-pressure stationary gas engines used for power generation, who also have to surmount the technical challenges of varying fuel quality and engine performance.

Kuwait Petroleums Q8Oils has been developing stationary engine oils for more than 25 years, but this is the first time it has received OEM approval for its Mahler G8 high-ash oil for natural gas engines, developed using its own additive technology.

In this segment, we develop products based on additive components, which is quite unique because many lubricant companies use market-general additive packages from additive suppliers, Joris van der List, the technical service manager at Q8Oils in the Netherlands, told LubesnGreases.

Traditionally, oils with more than 0.5 percent by weight sulfated ash were recommended for engines that only use polluted fuels with higher amounts of sulfur, chlorine and fluorine. These engines require lubricants that provide good oxidation stability in extreme temperatures. The downside is they produce higher amounts of sulfated ash that increases internal deposits and decreases the time between drains. Until now, only lubricants with up to 0.5 percent ash were recommended for natural gas engines.

With off-the-shelve packages, it is not possible to increase the ash level. Increasing some components, especially phosphorous, may affect exhaust gas treatment systems and cause problems such as catalyst poisoning, van der List explained. But as natural gas still represents a significant proportion of gas engine feedstock, Q8Oils has developed a new generation of oils with sulfated ash of 0.8 percent, but with low deposit tendency that keeps engines cleaner than more common low-to-mid-ash oils. For this type of new clean technology gas engine oil, the traditional rule more ash, more deposits does not apply, he said.

Although higher ash usually means higher levels of metallic elements in the oil from the additive package, which can burn and form ash, they are prevented from forming deposits on the engines components. This keeps critical areas such as piston top-ring grooves cleaner, cuts down on the lacquering of liners and extends drain intervals. Van der List said this is achieved by improved detergency, creating softer deposits and keeping more soot and oxidation byproducts dispersed in the oil instead of depositing on engine parts, which also helps to keep oil consumption low.

As the piston liner wears, oil consumption goes up, and so by developing lubricants that avoid wear, Q8 Mahler can help keep engines clean, lengthen drain intervals and improve the dispersion of smaller oxidation byproducts, which in turn extends oil filter life, with higher ash products than are normally recommended for these type of engines. Van der List said that soot and oxidation byproducts are kept small and dispersed and so do not clog the filter. The result is lower operational costs and improved efficiency.

Because the costs of downtime are very high, it has been a challenge to convince all stakeholders to test lubricants that are outside the historic limit values, for example, with a higher ash level, van der List said.

A cleaner engine that has piston liners in better condition also means users can operate the equipment at a higher efficiency rate for longer without having to reduce the power rating and so keep lube consumption lower.

In the search for improved oxidation stability offered by hydrotreated base stocks, lubricant companies have moved to API Group II and to products with lower base numbers. Q8Oils also aimed to improve oxidation stability, as well as, crucially, thermal stability in combination with solubility.

In our stationary gas engine range, we have moved to Group II and Group III based products. Q8 Mahler G-series is Group II based, but for our high-performance products like Q8 Mahler GR-series we have moved to Group III, van der List said.

It is not only about meeting oil specifications; we try to improve the correlation with practice in order to improve the quality of the oils. At the end of the day, the oil has to perform in the customer application, he added.