1. I've never had a performance car that used 5w20 oil. I know some of the current Jaguars run this weight oil so I suppose there is a precedent, but I've always thought of this weight oil as a fuel economy oil best used in cars like a Prius or Toyota. Are there any concerns or problems that some of you may have encountered (so far) using the factory spec'd Motorcraft 5w20? Anyone done a used oil analysis on this oil in their Mustang using the factory oil change interval? If so, how does the viscosity stand up?
5w20 has been recommended for quite some time now. I've done UOAs on both 5w-20 and (mostly) 5w-30 from Amsoil with intervals anywhere from 4,500 miles to 9,000 miles haven't had any abnormal results related to engine or oil wear.
2. Does Ford allow the use of 5w30 synthetic oil as long as it meets their oil spec, WSS-M2C 945-A?
Even though it's not specifically listed in the owners manual don't hesitate to use 5w-30. That's the oil I normally use, unless I accidentally buy 5w-20. Either way you'll be fine.
3. I'm guessing the factory fill is the 5w20 synthetic blend. What is the factory oil change interval for this oil? What is the factory recommended oil change interval if you use the Motorcraft full synthetic 5w20?
Either is acceptable. There doesn't appear to be any difference in the recommended intervals between the two. See link to owners manual below.
4. What is the normal operating oil temperature (for those of you that have an oil temp gauge)?
This would be interesting to know, as it's one of the ultimate deciding factors as to which viscosity is ideal.
5. I'm guessing that Ford uses an oil life monitor or oil condition sensor of some sort in the sump. Am I correct?
It does use an oil life monitor based on a computer algorithm. There is no oil condition sensor, despite what some people may think.
Most of your questions will be answered here: http://www.fordservicecontent.com/Fo...US_07_2014.pdf
Very good oil thread. Better than any you will find here: http://www.svtperformance.com/forums...302-UOA-thread