We all grow up with Oil Brand prejudices, usually ingrained in us by our fathers or our gear head friends! I was no different. So, a couple years ago I was tired of stressing about it and I wanted to put it all to rest and figure out what oil is the best oil to use in my 99 Cobra Mustang. First, I did research and found the best oil testing company, Blackstone Laboratories. I highly recommend everyone test their oil once in a while because it will give you a good idea of what is going on inside of your engine (i.e. is something wearing too much or a coolant leak, etc…) Anyway, I tested Amsoil Signature Series 5W-30 twice and Castrol Edge Syntec 5W-30 once. I wanted to see if Amsoil was really that much better, as they say, and could I actually go 25K between oil changes.
Well, what I found out is there is no real difference between Amsoil and Castrol. In fact, Blackstone put out a report shortly after based on a ton of tests that basically says there are only two oil requirements
1. The Oil has to be API (American Petroleum Institute) Certified
2. It must actually be flowing around in your engine lubricating the parts
That’s it! No worry or fuss about what brand, synthetic versus conventional or synthetic blend or not.
So my recommendation is to follow the 2 requirements above and change your oil and filter every 5K or so and you’ll be just fine. I like Wix filters. Also, I don’t have the guts to go 25K on any oil. I think it is good to get fresh oil in there every 5K just to flush out any metal particles that might be flowing around in my oil!
Reference
My Oil Tests Report 99 COBRA-053013-2