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dont be dumb, follow manufacturer recommendations

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Dec 14, 2013, 2:54 AM

Post #1 of 5 (3552 views)
dont be dumb, follow manufacturer recommendations Sign In

Funny story, I was like 15. I was driving my dads 96 chevy k1500 and i thought i would be nice and change the oil for him. well it called for 5-w30 and for one reason or another in my spontaneous adolescent mind i figured if 5-30 is good then 10-30 is better. im not positive i knew what it called for but without finding out i continued with the oil change. 10w and 5w are very different animals. the w meaning winter, i.e. temp. thins when it get colder, multigrade is great. well the result was; a 5.7 vortec sounds like a diesel until it warms up if you run 10w-30 through it in the winter months. he sold the truck later for unrelated reasons luckily.

Tom Greenleaf
Ultimate Carjunky / Moderator
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Dec 14, 2013, 3:22 AM

Post #2 of 5 (3544 views)
Re: dont be dumb, follow manufacturer recommendations Sign In

That's an all iron engine and really shouldn't have been that dramatic with that small change in low # viscosity. In general just use what was called for in anything rated to meet or exceed the OE specs,


Veteran / Moderator
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Dec 14, 2013, 9:38 AM

Post #3 of 5 (3529 views)
Re: dont be dumb, follow manufacturer recommendations Sign In

That's pretty close....

The weight or viscosity of and oil is actually resistance to flow, meaning the low numbers will flow more freely than the higher ones....The ones will the "W" have been tested at "colder" temps not winter temps but a temp less than 210. The ones with out the W have been tested at 210 degrees. So the W kicks in at cold start up which is one of the hardest times on an engine......

One mistake some people have made is thinking that if they have an oil leak....If they use a heavier weight oil, the leak will slow down........Doesn't work that way.....


Dec 17, 2013, 12:41 AM

Post #4 of 5 (3500 views)
Re: dont be dumb, follow manufacturer recommendations Sign In

isnt there a standard for the colder temperature used to check the viscosity? I was thinkin there was like 0F or 0C but maybe im losing my mind or my instructors were blowing smoke.

Hammer Time
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Dec 17, 2013, 3:43 AM

Post #5 of 5 (3493 views)
Re: dont be dumb, follow manufacturer recommendations Sign In

Taken from Wikipedia

The Society of Automotive Engineers (SAE) has established a numerical code system for grading motor oils according to their viscosity characteristics. SAE viscosity gradings include the following, from low to high viscosity: 0, 5, 10, 15, 20, 25, 30, 40, 50 or 60. The numbers 0, 5, 10, 15 and 25 are suffixed with the letter W, designating they are "winter" (not "weight") or cold-start viscosity, at lower temperature. The number 20 comes with or without a W, depending on whether it is being used to denote a cold or hot viscosity grade. The document SAE J300 defines the viscometrics related to these grades.
Kinematic viscosity is graded by measuring the time it takes for a standard amount of oil to flow through a standard orifice, at standard temperatures. The longer it takes, the higher the viscosity and thus higher SAE code.
The SAE has a separate viscosity rating system for gear, axle, and manual transmission oils, SAE J306, which should not be confused with engine oil viscosity. The higher numbers of a gear oil (e.g., 75W-140) do not mean that it has higher viscosity than an engine oil.


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(This post was edited by Hammer Time on Dec 17, 2013, 3:51 AM)

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