Oil is the last thing any diesel truck enthusiast wants to think about. But it's worth paying attention to, especially if the value of your engine and it's modifications is more valuable than the rest of the truck as a whole.
We've been running Amsoil synthetic fluids in the engine, transmission and differentials of our 2008 Ford 6.4L Power Stroke truck. And although it's not at finicky as the 6.0L and 7.3L when it comes to oil and engine oil changes, the 6.4L does operate best with high quality lubricants. Normally, we would stick with Ford Motorcraft oil on any Power Stroke, but we felt pretty confident with switching over to Amsoil synthetics.
There are a few key selling points that are appealing to us. We like the extended drain intervals. Amsoil claims that its 5W-40 Synthetic Diesel oil can run for up to three times longer than your truck's normal oil change interval when compared to petroleum-based oils. A lot of that depends on driving conditions, and if you went so far as to have your oil analyzed you could see the oil hold up for even longer. But at the high maintenance cost of operating a diesel pickup, Amsoil could save you money.
Now, we can't exactly pinpoint any exact change in fuel economy, but again, Amsoil claims its diesel oil can improve your truck's economy by up to three percent, and has data from an EPA Federal Test Procedure to back its claim. At 15 mpg, that's less than half a mile per gallon. Pretty negligible, but it's a gain nonetheless. We had too many different parts on and off our truck, from tuners to different tires, to be able to back up any kind of a gain related to the motor oil. But it certainly never got worse, if that says anything.
The Synthetic 5W-40 diesel oil is a low-sulfated ash blend that meets the requirements of 2007 and newer diesel engines with modern emissions restrictions. And it's an API CJ-4 oil.
We're also running Amsoil Synthetic Universal Automatic Transmission Fluid. And again, Amsoil has data from several certified tests where its ATF has offered double the service life of a petroleum ATF. And again, we can't really add to that other than to say so far, so good. But getting an extra few hundred hours of service life out of the transmission fluid means money in our pockets that won't have to be spent on a flush service. So if it works, why wouldn't we use it?