While I might not convert a newer, hard-to-work-on vehicle, I have converted several older cars to synthetic without problems: a 350 Chevy with 112,000 miles that I drove to 240,000 before selling; a 26-yr old Chrysler 383 with 78,000 miles that now has 135,000; and a 3/4 ton Suburban 454 at 140,000 miles that now has nearly 200,000 miles pulling an 8000-lb trailer. All were changed over to Mobil One 15w-50.
Consumption remained the same, or stabilized, or decreased, respectively.
Seal leaks were simply fixed, valve covers that were already leaking on the Chevy and Chrysler.
The temperature protection alone was worth it here in hot-as-hell Texas.
All had regular changes (3/3) except the Chrysler which sat up for five years with only a couple of changes and a few hundred miles of driving, and then went over a year without a change (9000 miles) prior to my taking possession.
The Chevy and Chrysler both required valve stem seal changes prior to switch over.
The 350 Chevy is long gone, the Suburban yanks that heavy trailer around in 100-F weather, and the Chrysler is a daily driver.
The Sub goes 6000-miles on changes with one conventional filter change at 3000. The Chrysler goes 4-months/4000-miles, sometimes 6/6 with a Mobil One filter.
The Chrysler was the only one to receive an engine flush due to low oil pressure at idle; then conventional oil for 500 miles, then cheap synthetic for 2000 miles before a change to Mobil One. Engine was partially disassembled at 100,000 to decarbon heads and valves, R&R timing chain and inspect bottom end. I found no evidence of problems, no sludge anywhere, only a light coat of varnish on cylinder block walls under intake manifold. This was more than 10,000 miles after a severe overheat (lost water pump and drove another 12 miles prior to shutdown). Engine uses approximately one quart per 4000.
While regular maintenance is key & experiences differ, synthetic is well worth any small pains when it comes to engine protection.
