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this depends on how the vehicle is used. if you do alot of short trips (10-15 mins or less),

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Davids,

Great info for Nestor! But... How does this affect filter life? To my knowledge, short trips don't allow the moisture to evaporate out, but don't add particulates... What am I forgetting?

Al

I thought you were an electrician based off the tone of your posts in the electrical forum.

i have done electrical apprentice work, not FULLY licensed though

From a quick google search:

5W30 versus 10W30

Virtually all new passenger vehicles sold in the U.S. use either 5W30 or 10W30 oil. The difference between the two is that the 5W30 flows better when cold, so if you live in a cold climate or operate your vehicle in a cold climate during the winter months, you should use 5W30 if it is the preferred oil for your vehicle. If you live in a sub-tropical climate and don't operate your vehicle in cold climates, then 10W30 is acceptable as long as the manufacturer specifies that it is permissible to use it.

Is there a disadvantage to using an oil that flows better when cold, i.e. 5W30 versus 10W30?

Sometimes, but usually not. The crux of the issue is this: the bigger the difference between the cold oil viscosity and the hot oil viscosity, the more the volume of viscosity modifiers and the less the volume of base stock. If you are good about following the manufacturer's recommended oil change interval then stick with the 5W30 if that is the preferred oil for your vehicle, even if 10W30 is acceptable in warmer climates. Older cars may specify 10W30 only. This is because they need a little more viscosity when cold to keep a protective film on the cylinder walls. There have been instances where the larger amount of viscosity modifiers that are present in 5W30 have broken down due to excessive heat and have left carbon deposits on the valves, but this is extremely rare. The proper fix would be to reduce the excessive heat, but the workaround was to use an oil with less viscosity modifiers.

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I think I'll go with what the manual says, which is 10W-30. If 5W-30 was listed as the "preferred oil" then yeah, no brainer, use it. But in my case 10W-30 is listed as the "preferred oil".

MTeator: I guess it goes without saying that Winnipeg would normally be considered a "cold climate" during the winter months, so I guess I should stick with the 5W30. Also, that's what it says to use on my engine's dip stick.

But, I'm glad I looked into this so that I have confidence that what I'm doing is right.

Just that little bit of investigating I did leads me to believe that most people know precious little about the oil and oil filters they use in their cars.

If they did, there wouldn't be so many stores selling Fram oil filters and synthetic engine oil. I probably agree with Cabin Connection that you rarely ever come close to filling an oil filter with dirt, but in my books, if Fram is making filters that they know are inferior to the competition (albeit sufficient to our needs), buying their filters is helping to support them in that practice. I think they should all make smaller filtration capacity filters and charge less for them.

Also, from what I read, synthetic oil is really of little value if you drive a normal car at moderate speeds under normal operating conditions. The reason why is that the oil gets contaminated with products of combustion. Every oil will initially keep those products of combustion in suspension in the oil, but once the oil is saturated with them, further driving with that oil will result in them precipitating on the metal surfaces inside the engine. The resulting gunk on the inside of the engine is called "sludge". The whole point in changing the oil in a car is to replace the oil before it becomes saturated with that sludge, thereby keeping the inside of the engine clean. Synthetic engine oils are only a little better at holding sludge in suspension than regular oils, but cost substantially more than regular oil. That tells me that the cost/benefit ratio of using synthetic oil is lousy. It costs more, doesn't last much longer and really isn't needed under normal circumstances.

I believe if more people knew this, very few of them would buy synthetic engine oil. I think the problem is that people PRESUME that if it costs more, it's better. In this case, it's better for the company selling the synthetic oil because they make more money. It's not much better for you or your car.

But, I expect there's LOTS of examples of that, and this is only one.

I'd only use synthetic if the car calls for extended oil change intervals. One of my vehicles takes 10 quarts of synthetic, but I can go up to 15K miles between changes. 10 quarts of regular oil every 3,000 miles is more expensive than 10 quarts of synthetic every 15K miles (though I usually hit the time limit before the miles limit.)