Both cars sound healthy, even the 92 with its consumption. For this summer I would put a HDEO (heavy duty engine oil) like chevron delo 15w40 in the 92. I used this oil in my 94 before switching to M1 5w40. It costs about $1.60 a quart at costco when you buy 24 quarts. Most places carry it for about $2/quart. I don't think synthetic would be apropriate in this situation due to the consumption. This is a "mixed fleet" oil meaning it is designed to work in both gasoline and diesel engines. Generally 15w40 oils are extremely well developed since most of its users are business fleets where wear = money and affects the bottom line. I would expect consumption to decrease with this oil but keep in mind its no magic bullet. I think you are safe to use 10w40 in the winter in most of the lower 48 states. If you like the results on the 92 you might consider running the same oil in both cars just for simplicity's sake.

My 94 burned about 1 quart every 2k miles on M1 10w30. After switching to 15w40 non synthetic consumption dropped to a little less than a quart every 5k miles. It remained the same with 5w40.
Good luck
Justin.
94 965 112k mies