Premium gas for winter time ? PZEV knock - Club Crosstrek | Subaru XV Crosstrek Forums
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Old 11-05-2019, 05:16 PM   #1
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Default Premium gas for winter time ? PZEV knock

One can easily understand how extremely high engine temperatures, summer heat, heavy loads, and high rpms ... might recommend the use of premium gas.

I found out that the Part of the PZEV system actually creates engine knock on extremely cold starts! The system is manipulating valve timing, injector timing and injected duration.

“ brief and subtle knock of the valves during cold starts, especially in low temperatures.”

I’m going to suggest that to protect yourself from these pollution controls one might consider premium fuel use in the winter.

Just a thought and maybe it makes sense and maybe it doesn’t.
Cheers

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Old 11-05-2019, 06:11 PM   #2
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At a compression ratio of 12.5 premium fuel would seem to be needed 100% of the time.
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Old 11-06-2019, 03:29 AM   #3
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It isn’t the engine by virtue of vvt can vary the valve timing so compression is only 10.5 to 1 and then somehow allow for 12.5 to 1 in the expansion stroke.
Efficient even on regular old crap gas. Even though the car runs nicer on premium.
PS: I still run Premium.
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