I just bought a 1981 Honda civic with 52,000 on the odo from an estate sell. I noticed the inside of the valve cover is caked with sludge so I plan to use Rotella 10w-30 conventional at short intervals for the first few oil changes. I then plan to follow up with a normal diet of GTX 10w-40 conventional. My question is will the GTX continue to clean if I use it strictly for the remainder of the cars life or is it just a plain conventional that advertises a lot of [censored]?