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Mixing oil grades?

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Old 04-11-2010, 03:56 PM
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Mixing oil grades?
I just finished changing my oil from 10W30 Castrol GTX to a thicker grade, 20W50. I have quite a few quarts of Castrol GTX 10W30 that's been sitting for about 10 years (if not more) that I only use to top off between oil changes. Is there any ill effect in doing so?
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Old 04-11-2010, 04:47 PM
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Originally Posted by SayNoToPistons
I just finished changing my oil from 10W30 Castrol GTX to a thicker grade, 20W50. I have quite a few quarts of Castrol GTX 10W30 that's been sitting for about 10 years (if not more) that I only use to top off between oil changes. Is there any ill effect in doing so?
It will work just fine (mixing oil grades/kind)

but I mean ... 10 years if not more ? ... throw them away ... stop being cheap ...
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Old 04-11-2010, 05:26 PM
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damn 10 years?!?!?!?!?! post up a pic of the bottles.
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Old 04-11-2010, 06:30 PM
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Eh, dude, don't... use... it. 10 years, wtf? Common sense here. Not bashing, but 10 years is a long time...
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Old 04-11-2010, 08:06 PM
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I have only used one two out of 12 quarts so far.

https://www.rx8club.com/showthread.p...ighlight=20w50
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Old 04-12-2010, 09:03 AM
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If they are 10 or more years old they are API classification SJ or older and do not meet the requirements of the engine.
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Old 04-12-2010, 10:36 AM
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Oil, being an organic compound, oxidizes and can decompose over time.

At the very least it could be several grades off its spec.
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Old 04-12-2010, 12:50 PM
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i wouldn't use em man .. why risk a 30,000 USD car for 15 dollars.
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