If you took half a day and snuck around some gas stations, grocery stores, or quicky mart type places, you can usually find stashes of SL/GF-3, which have 200 ppm more phosphorus then SM/GF-4. problem is, most places price it at over 4 bucks a quart.
One grocery store in my neighborhood has all the Chevron Supreme oils in SL/GF-3, to include 5w-40 synthetic, and high mileage.
The regular conventional is $3.99/quart, the high mileage is $4.99/quart, and the synthetic is $6.99/quart.