Quote:
Originally Posted by Railcarmover
.Improved Viscosity modifier properties means it resists breakdown when running multi viscosity oils..15-40 wt breaks down to 15w when the modifier fails,a higher stability factor means higher resistance to breakdown.
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During my 27+ years as a mechanic for Arizona Hiway Dept. we saw the opposite. We ran 15W-40 diesel oil in everything for many years to reduce inventory. When we were thinking of extending oil changes from 5,000 miles to 7,500 miles in cars and pickups, we did a lot of oil sampling. The oil in 350 Chevy pickups would often start to thicken after 5,000 miles if used hard. Seems like some samples came back as 50W!