Halfway between the two marks is just right. I keep a log book of date, mileage and anything I touch on the car. That way I know exactly how many miles I went between being at just right and being one quart low. You could easily be burning too much oil and never see smoke. Check it with engine hot and running and on level ground. BTW, older 911 oil level gauges are not that accurate. That's why I bought my 993
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