There are "high milage" oils out there. Just use one that is 5w30. Use a well known brand, not the cheap store brand. Discuss this with the shop at your next oil change.
As a general rule, if your engine isn't using more than a quart of oil between oil changes, there is no reason to increase viscosity. By making big changes in oils (say 5w30 to 20w50), the clearances must increase to allow proper flow at cold start up. If the clearance is not already there, then it will be created. In doing so the metals are "forced" to allow the clearance by wearing. Essentially, by prematurely increasing oil viscosity you run the risk of putting wear into your engine that did not previously exist. The increased oil viscosity will actually cause wear. Always increase oil viscosity in small increments until oil consumption is under control.
I would use "straight 30 weight" it is on the shelf for sale for a reason
for older engines.........
use non detergent 30 weight oil,...... this oil will not clean as it moves around as the older engine is gummed up Little and detergent oil will get dirty quicker. detergent oil is when you buy the buy the vehicle new and you all ways buy detergent to keep it clean inside.