I change oil every 4,000 to 5,000 on our e450 based Vegas. Get Motorcraft oil and filter at Walmart. Easy job and I grease all fittings I can find.
I live in Florida when temp swings cause moisture buildup in everything. My Chevy small blocks in drag cars take 10 minutes of steam out breathers to get accumulated moisture out of oil.
I have never had an oil related breakdown in any engine and most of my street vehicles last over 200,000 miles. The relatively low cost of oil changes make it very attractive for longevity. Short idle periods are not good, if you start it allow it to run up to full temperature a bit.
When we bought our RV, it was used and over a year old with less than 2,000 miles. It still had original oil and filter from factory. It was reasonably clean but I wanted my own baseline.
Only my opinion, but it has worked for me.
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