I agree with the guys, continue using whatever got it to 200K miles.
I'd also add, if it's leaking/weeping at some seals, maybe consider a "High Mileage" formula, in the brand of oil you've been using, as it's seal softners could maybe help slow any leaking, or maybe even stop a weep.
If it's burning some oil, then look to your brands recipe that offers the best volitility, or lowest evaporation loss, & lowest ash number, as the first two may help cut consumption & the last could help cut combustion chamber deposits, if it's burning some oil.
One added benefit of diesel rated oil, is it keeps engines clean that experience a lot of idling, plus it holds dirt and soot in suspension very well.
If nothing else, if you use a 10w30 oil, add a quart of diesel rated oil (10w30) as your last quart.
I have no problems with diesel rated oils used in any gasoline engine that does not have a catalytic converter. On a emmsion controlled engine that has a CAT and oxygen sensor, I would limit the diesel rated oil to one quart of total capacity.
If it's not burning any oil stick with what you've got. If it does burn oil, try moving up incrementally until the problem is fixed. Start with 10W30, then go 10W40, etc. until it's not buring as much oil.