You'll find that there are more answers to this question than there are numbers in pi.
I personally like three quarts of Havoline full synthetic 5w-30, one quart of Lucas, and a Bosch filter. (the one with the nice, metal anti-drainback valve) I haven't heard my lifters chatter since I started using this combination about
2 years ago.
Paco
97 Montego Blue Miata
91 Toyota Previa
77 Suzuki RE5
Unless you have forced induction, I would stay with normal 10-W30 oil and a reasonable change schedule (eg, every 5k miles.) Whether anything better is worth it? I doubt it, but I do not believe there is strong data either way or the other.
I would think the "Clean" oil brand would beat out the "Dirty" oil brand. Whether there are any other significant differences between established oil brands?
Putting an old engine on synthetic oil has been a problem for some.
Listen to what everyone says, make a decision and do it. The most important message to take away is this: change the oil and filter regularly. That appears to be the key to making engines last a very long time.
I have used Mazda filters exclusively, but am going to start using Proline as it's too much of a pain to get to the Mazda dealer. Other cars we have had did just fine with aftermarket filters.
Ken '90 White "B" nearing the next oil change at 168K miles, dino only and still on the original clutch.
For that matter, my friend has been using dino (Quaker State) exclusively in his '94 Cherokee. He's over 304k now with no engine trouble at all (needed a trans rebuild at 275k due to hauling oversized trailers through the mountains of WV).
I still stick to Mobil 1 and Mazda filters. I've been using 10W30 but noted the comment about forced induction. I'm running a Greddy w/5lbs boost in my '91. Don't really need (though will eventually install) an intercooler at that pressure, but would like to hear comments on what weight oil might be best. The engine runs at a decent temperature, but I've installed a heat shield over the turbo to cut down on the steam billowing from my hood when I stop on a rainy day.
Otherwise, the engine purrs at 130k, growls pleasantly through the Flyin Miata dual turbo exhaust, and has enough punch to keep the grin on my face.
D>Listen to what everyone says, make a decision and do it. The most important
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