Yes, it was not 100% beef tallow, but a blend, and it was truly what make McD’s what they were, the buttery delicious fries it produced. In the 80s they went to the full hydrogenated vegetable oils to avoid the saturated fat, and basically poisoned millions with unhealthy trans fat.... since they have backed off, and there is tallow in the oil again, but its not the original formula...
McD’s has a LOT of problems, but if they returned to Formula 47 I guarantee they would see their sales climb.