40 CFR §1065.745

1. (a)You may use commercially available antifreeze mixtures or other coolants that will be used in your engine in use.
2. (b)For laboratory testing of liquid-cooled engines, you may use water with or without rust inhibitors.
3. (c)For coolants allowed in paragraphs (a) and (b) of this section, you may use rust inhibitors and additives required for lubricity, up to the levels that the additive manufacturer recommends.