fantozi:
You're going to get a ton of opinions here but all I can tell you is that I've used nothing but standard Mobil 10-30 oil in my 1990 5.0 since I bought it brand-new in '90. I changed the original oil & filter at 1000 miles, then changed them both again at 2000.
I've changed the oil and filter (Ford Motorcraft) every 2000 miles - without exception - since then.
When I pulled my valve covers (to change the gaskets) @ 87,000 miles, the heads were shiny clean; no goo, not even discoloration except a tiny bit in one corner and that was very light. My lifters are quiet and my oil pressure remains at 50-60 lbs. on a hot day under a load.
This may not prove Mobil is 'the best' oil, as I change my oil frequently, but I've raced this 5.0, it's seen triple digits fairly often and I've run in hot weather (90 degrees plus) and with all that over eleven years I've never seen the oil pressure drop more than 10 pounds (to around 45) under the worst conditions. Even at 112,000 miles, it doesn't burn oil, no lifter noises and the oil pressure remains constant and normal.
I like Mobil 10-30 and I recommend it.
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