I can't remember where I got that from. I wanna say from a haynes manual or possibly from some kinda capacities sheet here. I think it noted an ammount rather than a mix ratio. I wanna say that it was 1 7/8 gallons coolant for my 97 5.2 2wd and fill the rest with water. I went through this because I was fighting a really sucky heater and after flushing the core and replacing thermostats and Dipping and rodding the radiator my heater still sucked, and my temps still seemed low by the factory guage. I then started looking at mixtures knowing that the ammount of coolant affects the insulating properties of the water. I know that too much antifreeze can cause overheating and we all know what too little leads to. I started mixing to what it suggested and my heater did get better but I still dont feel like it's as good as it should be.

 

I'm guessing that would be very close to 50/50, if not exactly 50/50. Neither the 2000 nor the 2001 FSMs that I have list the cooling system capacity for the 5.2L, but they do list it for the 3.9L (14 qts. both years) and the 5.9L (14.3 qts. in '00 and 14.6 qts. in '01), so the cooling system capacity for the '97 318 is probably in the range of 14 to 15 qts.

1 7/8 gallons is half of 3 3/4 gallons (15 qts.). If the '97 318 cooling system only held 14 qts., then 1 7/8 gallons of coolant would be about a 54/46 mixture, which is still in the acceptable range of mixtures.