how to read oil pressure gauge in a 07 tahoe?

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Hey all, just a question on the oil pressure gauge in my 07' tahoe, it is in Kpa's and my question is when not running the needle sits at zero obviously LOL! But what would the line between zero and half be in kpa's? Half is 275 kpa's when my engine is up to temp my needle sits right at the front edge of the 2 in the 275 on idle, so I am curious what the line is before the 275 and what the line after the 275 would be? Thanks for any info.