Originally Posted By: kschachn
Originally Posted By: Danh
In the event of an engine failure the dealer/manufacturer could send the oil to a lab for analysis. If your car is spec'd for 0w-20 and the 100C viscosity came back at 11.0 cSt, they could make it an issue. I realize this scenario is unlikely but not impossible, especially with a $5,000 warranty claim is on the line.
OK but what's the difference if you get there by blending oils or by using a heavier one to start with? The end result is the same.
And does anyone really know if your warranty is actually voided by using a heavier oil than specified? Does it actually say in owner's manuals that use of a more viscous grade will violate the terms of a warranty?
Blending could get viscosity to a point where its viscosity when new wasn't evident. For example, if an 0w-20/30 blend started at 9.7 (rather than a straight 0w-20's 8.7), a lab would be hard-pressed to conclude it was not a 0w-20 to start, especially after a bit of use and fuel dilution. Starting with an 0w30 at 10.9 would make it easier to conclude a non-approved viscosity was used.
I know we're getting into the weeds here and each manufacturer may be different. Honda, for example, requires specific fluids for transmissions and differentials. But 0w-20 motor oil is only "recommended". Exactly what this means for the warranty is unclear, to me at least. I suspect most dealers just look at general engine cleanliness and maybe maintenance logs, so maybe it's a moot point. But for the risk-averse...