Originally Posted by
swingtan
Oil, like many other consumables, needs to be chosen to suit what the car is being used for.
Personally, I don't like 10W60 as it doesn't lend its self well for how I generally use my car. Putting it simply, 10W60 is a thick oil (compared to ssay a 5W40). When cold, the oil flows less and pressures are higher until the oil has reached normal operating temps. If you only drive short distances, the oil may rarely reach optimal temps, so a thicker oil will always remain in its "thick" state. Obviously, if you're racing the engine, you've allowed the engine, all fluids and the whole drive train to come up to temp, so it's much less of an issue and the added protection from the thicker oil is warranted.
Continuing with the "thick oil" issues, the thicker the oil is, the worse it is at lubricating some components when cold. For example, the cylinder walls, piston skirts and even the lifter rollers all rely on oil splashed off the spinning crank shaft. If the oil is thick and sticky and the RPM is low, the amount of oil reaching the cylinder walls is significantly reduced. This is why I'm not a fan of leaving a car idling in the drive to "warm up" before driving. Oh, and don't forget that if you run a cooler thermostat, the oil takes longer to reach normal operating temp. To add to the confusion, cars up north that see higher average temps would be a better fit for a thicker oil. A quick test is to grab a cup of fresh oil and stick it in the fridge over night. Take it out in the morning and see how it flows at 4'C.
There's lots of other factors to consider, bearing clearances, peak oil pressures, driving style and durations, age of the engine and amounts of wear. No one answer fits all cases. I've tried a number of different viscosities over the years and am currently running a 10W40, which I think is a tad thin for my use. I normally run a 15W50 semi-synthetic and will be moving back to that as it is what seems to work best (doing my own debris checks at oil changes). I've run full synthetic 10W60 and while it was OK, I found it increased lifter noise and the cost difference over the 15W50 was quite high.
I'm not against 10W60, if your engine requires that viscosity then it's the right one to use. Most cars probably don't need it and some should run a thinner grade, it's all "horses for courses". I've used Penzoil Racing 50 in one motor, but it was for a specific purpose and was given a good 30min of warm up before being really "driven".
