Well it is about time to change my oil on my 91 civic with 297k miles standard. I use Castrol GTX with a Purolator classic oil filter. I wanted to try Valvoline this time around because last time I used valvoline I burned less oil, so I thought might aswell try it again to see if it just wasn't luck. At the store I am looking at they have Valvoline Max life for like 4 bucks more and a pure one filter. Since its one of those high mileage oil would it be okay to keep switching between standard conventional and high mileage conventional? What about Syn blend? I was looking at one time motorcraft since they sell it at my local walmart, would that be okay to keep switching between?