Issue link: http://read.dmtmag.com/i/859318
Engine Oils Background & Properties castrol.com/GPS 800 255 4417 May 2025 GPS Industry Specifications finished lubricant. Additives can react differently with each category of base oil. ree easily discernible characteristics in base stocks are sulfur content, saturation, and viscosity index. e measurement of these features gives insight into ultimate finished product benefits. Sulfur Content Sulfur content relates directly to many performance characteristics of the base stock. Sulfur negatively impacts catalysts in aertreatment systems and can impact seal compatibility, oxidation, and deposit performance. Total sulfur in CK-4 oils Is limited to 4000 ppm max. Advanced refining and finishing processes remove nearly all of the sulfur in a base oil. Saturation Saturation refers to the amount of base oil molecules that have no chemically active double bonds. is is an important characteristic in a base oil because these double bonds can be easily broken to allow hydrocarbon molecules to react with one another or oxygen or nitro-oxidized molecules. e result is oxidation in the base oil, which leads to oil thickening, deposits, and breakdown in finished lubricants. Highly saturated base oils, like Group II stocks, have been treated with hydrogen gas during refining. is process forces hydrogen through the oil and causes it to react with the double bonds. is saturates the molecule with hydrogen, thus eliminating opportunities for oxygen to attach and making the base oil more oxidation resistant. Viscosity index Viscosity index (VI) may be one of the single most important performance measures in both a base oil and finished lubricant. VI is the measure of a change in viscosity relative to a change in temperature. Base oils with high VIs (over 100) experience less change in viscosity due to temperature. High VI finished lubricants, such as multi-viscosity engine oils, offer improved protection, pumpability, efficiency, and oil consumption benefits over lower VI lubricants. Base Oil Groups: Characteristics Currently, the media, the industry, and oil marketers are playing up the benefits of Group II and higher base stocks. Here is a review of the characteristics of each base oil group: • Group I base oils have VIs of 80 to 120 and were the original, traditional engine oil base stock, but are not common in modern engine lubricants. Group I base oils have more sulfur and less saturates than Group II, III, or IV fluids. e performance of finished lubricants blended with Group I base oils is largely dependent upon the quality of the additive package. • Group II base oils are known for their excellent deposit control and high level of saturates, which makes them more oxidation resistant. ey typically have VIs of 95 up to 120 and rely heavily on additives to Aromatics Naphthenics Group I Group II Group III Group IV Group V % Saturates >99% >90% 0% Better Oxidation Stability Improved Soot Control Higher Viscosity Index API Base Oil Groups A20 C: ::::::::, c:::: ill ecastrof