Mobil GEO 15w-40 is Natural Gas Engine Oil for vehicular applications. Mobil GEO series is a premium engine oil line manufactured by Mobil Lubricants. "GEO" refers to "Gas Engine Oil" because it is specially formulated for use in vehicles that run off compressed natural gas (CNG) and liquid natural gas (LNG). 15w-40 is the thickness of the oil based on Society of Automotive Engineers (SAE) standards.
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