Originally Posted By: Vlad_the_Russian
My friend has a small 2-truck fleet of 2012 F250s with the 6.2L. Well in the summer both got new batteries on the same day, and got oil changes on the same day. The only difference is the oil grade. Even the oil filter was the same Motorcraft. First truck got a dose of Rotella T6 0w40, and the second truck received Rotella 15w40. No big difference in summer, except slightly worse fuel economy on the 15w40 Rotella. But yesterday he had the first 50°F start on both trucks with those oils, and that is where we really saw the difference... Not even close to freezing, but the 15w40 struggled for nearly 7-10 seconds before it started, and then continued with the valvetrain noise for a few seconds, while the 0w40 cranked right up with no weird noises. Both have 4k miles on OCIs and both sat for 8hrs before start up.
Next OCI, switch the oils between trucks, it will be a good comparison and then the data will be more a accurate.
But...0w40 FTW in any cooler temperatures.
