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-   -   Clarify oil weight/viscosity (http://www.jeepgarage.org/f107/clarify-oil-weight-viscosity-38393.html)

mixer440 03-05-2012 04:04 PM

Clarify oil weight/viscosity
 
Have V6 3.6 Laredo
Owners manual says 5/30
Dealer says they use 5/20

Is there an issue with this and why would I want either ?

Ratchet 03-05-2012 04:43 PM

Re: Clarify oil weight/viscosity
 
The grade of oil depends on the temperature in your area. Good rule of thumb is to keep it simple and follow the recomendations in the manual.

mixer440 03-05-2012 06:10 PM

Re: Clarify oil weight/viscosity
 
I agree with you on sticking to what the owners manual/oil cap says (5w30)

Interestingly, if you talk with the oil companies, the higher value (in this case 20 or 30) is really about engine temperature according to them.

Of course, I don't pretend to know all the engineering with the engines in these babies, perhaps the 3.6L Jeep engines run hot and have thinner walls, and the 5.7L don't, or need the 5w20 for some other reason. But it seems to me that for a 3.6L a 20 weight would be thinner and therefore reduce friction and maybe provide an insignificant amount of better mpg. Also, a bit nosier engine as well.
On the other hand the 30 weight would be thicker, better for higher engine temps, thinner walls, less engine noise, perhaps less mpg.

Hundreds of other posts also have "their" own opinion----either way.

???
Since the dealer put in 5w20, now I have to decide whether or not to have them change it out to 5w30 (the recommended one) or just leave it alone for a few thousand miles.
???

Ratchet 03-05-2012 08:08 PM

Re: Clarify oil weight/viscosity
 
Depending on the climate in your location and your current mileage, I can't truthfully say anything certain, but either way, I am quite confident that uding the 5W20 for a bit won't cause any premature damage/wear.

Frango100 03-05-2012 09:41 PM

Re: Clarify oil weight/viscosity
 
Engine temperature should not have any influence on choosing which grade of oil to use (on normal liquid cooled cars), since the normal operating temperature is kept at or around 100C (212 F) by the engine cooling system, independent of the climate.
The first figure of the grade shows the viscosity when cold, the figure after the W the viscosity when at operating temperature. 5 means that the oil has the same viscosity as a straight 5 oil when cold, its not the actual viscosity number. Because 90 % of engine wear occurs during start-up with a cold engine, due to lack of lubrication, it is important to have a thin oil, which will go fast to all lubrication points inside the engine. A grade 0W-- oil is the best at start-up, because it will reach all points as fast as possible.
The 20 or 30 after the W shows the grade at operating temperature, so the oil has a viscosity which a straight 20 or 30 oil will have at operating temperature.
The grade 20 oil is thinner then the grade 30 oil. Thinner means it flows easier and causes less resistance, resulting in a lower fuel usage. On the other hand, it will also lower the oil pressure inside the engine and could easier cause metal to metal contact in bearings under extreme conditions. But for normal use, there should be no problem to use a 5W20 instead of a 5W30.

mixer440 03-05-2012 09:51 PM

Re: Clarify oil weight/viscosity-warranty ?
 
Excellent comments and understanding Frango. Thanks.

Now, here's perhaps a bigger question. Let's say you choose to use whatever oil you want (within reason). Now we all know that an engine isn't going to seize up on some of these minor oil differences under normal conditions, but what if you did have a problem, would your warranty be void ?

I suppose that if "no one" ever knew but you, then they would probably never know you used a different type of oil, but what if they did know that: say, you used 0w20 or 5w20 vs recommended. Would they honor the warranty ?

peckmv 03-06-2012 12:54 PM

Re: Clarify oil weight/viscosity-warranty ?
 
Quote:

Originally Posted by mixer440 (Post 587460)
Excellent comments and understanding Frango. Thanks.

Now, here's perhaps a bigger question. Let's say you choose to use whatever oil you want (within reason). Now we all know that an engine isn't going to seize up on some of these minor oil differences under normal conditions, but what if you did have a problem, would your warranty be void ?

I suppose that if "no one" ever knew but you, then they would probably never know you used a different type of oil, but what if they did know that: say, you used 0w20 or 5w20 vs recommended. Would they honor the warranty ?

The chance of you seizing your engine with oil in it is quite low. If you use an oil that the manufacturer does not recommend, and if something goes wrong that is caused by the wrong oil it won't be covered by the manufacturers warranty. They can tell what oil you used by taking a sample and having it tested. Bottom line....don't deviate from the manual.:slapfight:

hububub46 03-06-2012 04:37 PM

Re: Clarify oil weight/viscosity
 
The 5w /20 is mandatory for the 5.7 MDS. the V-6 states 5w/30. I do not see OR 5w/20. They have bulk oil at this dealership and that is what they use for their 15.99 oil change special. They DO have the other oil in the bottle, go to the parts department and ask to buy 6 qts of the 5w/30, tell the parts guy to charge it to the service desk and walk over and plop it down on his counter. DO NOT LET THEM put the wrong oil in your engine!!!


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