Start by protecting dye stability
Dark and bright garments can lose or transfer dye, especially when new. Cold water is a conservative starting point for many everyday dark loads and pairs well with sorting new or unstable colors away from light laundry.
Heavy soil does not automatically mean hot water
Use a compatible pretreatment and an appropriate cycle before jumping to heat. Some durable dark garments may allow warmer water, but a higher temperature can increase color-change risk and is never a substitute for checking the care label.
Fabric still controls the limit
Dark denim, dark cotton, black polyester and a dark wool sweater do not share one care method. Sort by both color and fabric needs, and use the most restrictive instruction in a mixed load.
Connect temperature with sorting
Use the Wash Together Checker when you are deciding whether darks can share a load with lighter items, and use the Wash Temperature Finder for the reviewed temperature starting point after the load is properly sorted.
Garment care labels, appliance manuals and laundry-product directions can be more specific than a general guide. Use them when they set a tighter limit.