Synthetic Oil versus Regular

Vulcan Rider wrote, "IF the present oil doesn't show any signs of leaking after a couple of thousand miles, keep using it. There are NO downsides to continuing except maybe for a few cents difference in cost."

What would cause the leak? And, where would it be leaking?

Also, THANKS to everyone who has responded. I certainly have food for thought.

Synthetic oil viscosity increases with heat and fossil oil viscosity decreases with heat. I was a crew chief for a race truck team. New engine with 50W racing oil in a 17 qt dry sump system and low oil pressure lite came on at lap 1.5. Panic city with $25K motor. Mobil 1 team in pits next to us gave us 2 cases of Mobil 1. Changed oil and the 2 filters and never saw the warning lite again that day. BTW we finished last and didn't qualify for the main. I run Mobil 1 turbodiesel oil in my cummins, Mobil 1 10W30 in my craftsman riding mower and Mobil 1 15W50 in my 468 cu inch jet boat.

mikeleblanc413 wrote:

What would cause the leak? And, where would it be leaking?

Old engines leak.....and burn oil.

The leaks generally are from leaking gaskets or seals in places like a valve cover gasket because they dry out and shrink with age.

Sometimes the oil burning is because of worn valve guide seals.

IF.....an old engine shows no signs of leaking (oil spots on the garage floor) AND it doesn't "use" much oil between changes, then "high mileage" oil is not needed and actually can accelerate the wear on good valve guide seals.

It's good stuff but not to be used if the things it is supposed to help cure are NOT present. It helps make the last years of a high mileage engine easier to live with but eventually that too stops working and it will leak or belch smoke again.

No reason not to continue with synthetic but shouldn't be using "high mileage" oil unless you really need it.

As Vulcanrider said if it does not leak keep using it. My experience is mixed. When I switched to Syn oil in the MH an old 454 with 50,000 miles I had no trouble. I decided why buy 3 different oils so I used the same 10-30 wt oil in the genset and tow car. The tow car 2002 Toyota Corolla leaked at the pan gasket, and I re-tighten it 3 times and 4 oil changes with regular oil before it stopped leaking. The genset, because of less usage did not show up until the following year or so and just got worse. I could not tell where the leak was coming from. I switched back to regular oil and the leak is slowing down but is still leaking. I might try a blend first on an older eng with a lot of miles and look for leaks. I have 104 k miles on the 454 and it runs great with syn. I saw no difference in MPG or any difference in heat reduction using it.