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Originally Posted by Eldi Z
Since GM confirms 5W to be the correct specification in low ambient temps for the LT1 engine, which BtW has not changed its material since the introduction in the C7 2014, I cannot understand the issue with using this viscosity rating, especially in warmer ambient regions. The real-world advantage of the 0W oils in reducing engine wear in the long term should be negligible.
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I don't know about earlier cars, but the manual for my 2020 says:
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Originally Posted by Chevrolet
Use SAE 0W-40 viscosity grade engine oil for the LT1 and LT4 engines. When selecting an oil of the appropriate viscosity grade, it is
recommended to select an oil of the correct specification. See “Specification” earlier in this section. If 0W-40 dexos2 oil is not available, SAE 5W-30 dexos1 full synthetic engine oil may be used for street use.
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It doesn't give different recommendations for different climates. It also says that 0w-40 dexos2 is the factory fill (which I assume means it is Mobil 1), and that this is recommended for track use on an LT1 or non-ZLE LT4. I never said there was "an issue" with using a 5w-40 oil. I'm saying that the
most protection for an LT1 in normal street use is given by 0w-40 oil. If for some reason you don't want to use that, despite the factory recommendation, I am sure that your engine won't seize tomorrow. I just can't see a reason
not to use it.
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Talking about Group 3 Vs. Group 4 oils: Do you have any proof that the Exxon-Mobil stuff (0W40 ESP formula) is actually based on a Group 4 and not a Group 3 ("heavily hydro-cracked") fluid?
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I do not.
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You can get extremely high quality oils which are Group3 (where the additive package is superior) than I.E. mediocre quality Group4 base oils (in which the additive package is not as good / efficient).
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I'm sure that's true.