How detrimental is it to...

Red__Zed

The need to warm the engine up stems primarily from the desire to get the motor oil up to temp. If you wail on your car while it's cold, you are essentially running 5 weight oil in the engine...

ImportConvert

No, you're running something thick as syrup and it doesn't lubricate as well, or pump NEARLY as well. In other words, you have more pressure at the pump and less up top and over the bearings.

No, you won't blow your car up the first time, but it's not a good habit at all. That is why many high-end cars have tach's that adapt to the running temp like the M series, etc.

Red__Zed

What exactly are you disagreeing with in my post?

ImportConvert

I am disagreeing with the way you say "running the engine with 5-weight oil".

That is deceptive in that the oil is very thick when cold. cSt of most "X"-30 weight oils is around 60 when cold. When you heat them up, the cSt drops to around 9-11.

The way you presented it makes it sound like oil is thinner when its cold.

Red__Zed

I apologize if my comment caused confusion. I meant it behaves as a cold 5W oil, giving it a (slightly) higher viscosity. I guess I should have fleshed that comment out more.


Not sure where you get the 60cSt number. It's usually below 20, at least for a 5W oil.

Viscosity Charts

ChrisSlicks

Because it isn't an SAE-5 oil, it is an oil blend. A 5W30 isn't going to perform the same as a SAE-5 or an SAE-30, most of the time it is somewhere in between. It's properties are such that it can pass the minimum test for SAE-30, however there actually isn't any standardized test for Winter weight and most oils certainly wouldn't pass the test of SAE-5.

The viscosity numbers quoted (60 cSt @ 100F) is an average from actual manufacturer test data. On a cold start on a cold day it will be slightly higher, probably around 80-90.

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Mt Tam I am

I HAVE NO CLUE AS TO WHAT I AM DOING. With that said, I still give the car a 30 second warm up and then take it easy for the first mile, check where the temp is, and determine wether or not to raise the rev's.

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Red__Zed

Maybe I'm confused. I was under the impression that an SAE 5W-30 met the 5W low temp test, as well as the 30 weight 100C test, and behaved as in the following chart:



I know there's a lot of misinformation out there though, and I probably got some of it-- I won't pretend to know everything about oil. I am genuinely curious about how they rate the winter oils, if there is no standardized test. I was under the impression that the timed orifice method was used for the 100C test, and then it had to meet a standard at 40C, based on the cranking/pumping characteristics.