The final approach to laundry prewashes is that of the degreaser.
This shouldn’t surprise us, as this is exactly how dry cleaners work, and how the older (and better performing) laundry prewashes work.
The reason simply is that if a stain doesn’t wash out, then very often it is because it is oil-based, and so a degreaser will remove it.
So then what’s the difference between these older laundry prewashes and automotive degreasers? Or to put it another way, can you use automotive degreasers as laundry prewashes?
The main difference between them is the washout. Laundry prewashes were designed to wash out completely in the wash, with no residual solvent smell, and are much more sophisticated formulas.
A recent change in automotive prewashes, however, is the switch away from solvent based formulas to water based formulas, based on alkaline silicates. These products of course have no solvent smell and wash out well, and are an excellent option as a laundry prewash.
So use degreasers based on alkaline salts (such as Diggers or Kenco) for general prewashing, and enzyme based cleaners such as White King for food based stains