Even the venerable Ford 7.3 recommended nitrate tests. Ford changed coolants for 2011; the tests and the treatments are all different. Using the wrong treatments will require a flush.
Painted Horse on Diesel Stop says it well:
Your coolant has a 105,000 mile life expectancy. You can add the coolant additive twice during that life. If you divide that out, Its about 35,000 and 70,000 miles. Chances are with this 1st message, your coolant will be fine and the computer is just the routine reminders. ( Every 13,000-15,000 miles)
The 1st test is for Nitrates. Our engines use an OAT (Organic Acid Technolgy) based coolant. There should never be any Nitrates. Past Powerstroke engines used a Nitrate based antifreeze. So this test is basically to make sure that nobody has added any of the old style antifreeze or additives to your coolant. It uses the same test strips the old engines used, Except you look for ZERO instead of a positive amount of nitrates. If you find ANY Nitrates, You flush and refill the coolant system.
The 2nd test is for freeze protection. I think it reads about -50°. If you don't have sufficient protection for your area of the country, You increase the antifreeze ratio. Again make sure you add a OAT antifreeze. This again is on the same test strip as previous antifreeze test strips.
The 3rd test is for Contamination. This is a little bit more of a test. Take the sample, drop a tablet in and disolve it, test with special test strip. This is all new for the 6.7L and any engine using the new OAT based antifreeze. If you fail this test, You can add a rejuvinator or additive. (VC-12) Do not confuse this additive with the older additive used on Nitrate based coolants. You can add this additive twice during the coolants life.
You have two cooling systems on your truck, The coolant does not intermix between the two. Hence the need to test both systems, You can have one coolant fail and the other be just fine. You may need to add the additive to both tanks or just one. If you need to add to both tanks, You will need more than 1 bottle.
