Yes different oils can give much different pressure readings. It would help to know exactly which oils you are talking about- viscosity ratings and whether conventional or synthetic. Also some of the zinc additives increase oil viscosity a good bit, so would be good to know what you are using for that too.
10 psi at idle will not hurt anything but I would select an oil that keeps idle pressure above 20. If it takes a heavy viscosity oil to get there or there is a sudden change in pressure using the same oil then there is a problem somewhere.
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1969 Lemans vert, matador red, 462 CI, 3.07 12-bolt posi
1974 455 TA, admiralty blue/red interior HPP "cover car" - sold
"The best way to show a car is to drive it"
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