The engine temperature gauge rises to 3/4

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The engine temperature gauge rises to 3/4 when driving over 60-70 MPH, but its on 1/2 most of the time but moving rapidly over and under very fast, tried to add coolant fluid and get all the air out of the radiator but still the same, that happened after changing the oil yesterday the same 5 - 20 but a different brand that i don't recall,