First of all, Ford definitely can deny you warranty coverage by making you prove that the lubricant used is equal to the one they recommend. Assuming that they PTU lubricant is actually the US Lubricants, 300 Waylube, your Redline won't measure up (it's why is so much less expenseve.) But it may be sufficient.
Don't take the word of a competitor. Get it in writing from Ford. For example, i refused to allow my local Lincoln dealer to switch my MKX from yellow coolant to the new green; until I got a printout of an email from the local Ford district administrator.