Mars

Cold oil

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I use 30 weight oil in my 30 cf. Started it yesterday for less than a minute, shutting it off when I wasn't getting an oil pressure reading. It was bearly 30 degrees outside, so I'm thinking the oil was just too thick to flow well. Make sense?

 

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30 weight oil should still pump if the oil pump is working. The difference you should see is higher pressure on the gauge.

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Might the gauge be affected? Being a mechanical pump, how likely is a failure?

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How about disconnecting the guage line at the block and briefly spinning the engine over to see if oil comes out ? Keep some rag close by !!

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You might not get much oil pressure at idle, esp. when pumping "thick" oil.

 

Multi-grade oils are formulated especially for situations such as you describe. 0W or 5W-30 would be better at those temperatures, when it behaves as SAE 0 or SAE 5 respectively and the pump can more easily pump it. When warm, it behaves as SAE 30. An oil pump doesn't move much "thick" oil, such as you describe.

 

The idea of an oil that behaves like a lower viscosity oil at low temperatures is that the oil pressure comes up more quickly and circulation is achieved more quickly than with a "thick" or higher viscosity oil. Most wear occurs at cold startup so the faster the oil circulates the better. Basically, the flatter the oil's viscosity curve against temperature the better.

 

For minimising wear, ANY synthetic oil is better than ALL mineral oils.

 

Single grade oils such as you describe are for lawn mowers, IMO. And it is not "30 weight" it is "SAE 30", which is a standard viscosity band.

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You should not use straight weight oil in winter conditions especially 30 weight. The reason is coagulation, the oil will not flow the colder it gets and will allow the bearings to score. The only way to use straight weight oil is to keep the engine warm (engine heater, light under the hood etc etc). As far as synthetic oil is concerned  Amsoil is the best product I know of. It is the only oil the F.A.A. approves for aircraft because of high altitudes (very cold conditions) This oil coagulates around 65 degrees below zero it also maintains a higher boiling point so it doesn't break down like mineral oils do. This oil you can actually change the filter only and just top off this oil. I've seen engines that have gone over 100,000 miles without having a 'full' oil change and the insides of the engine look like brand new. It's a little expensive but worth it. Do some research on it see what you think. 

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On 20/03/2018 at 12:08 PM, Mars said:

Are there synthetics that compare to detergent oils?

No. As I said, they are all far better than any mineral oil. Heed retiredmechanic's words, they are good!

 

Ref viscosity curves, I suggest you read Richard Widman's paper on oil. It is specific to his 1960-ish Corvair but the principles apply to oil for most old cars. You will get a bit of a grip in viscosity too. It took me three readings to absorb it.

http://www.widman.biz/Corvair/English/Links/Oil.html

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