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Thread: Engine Oil Question. Calling NinetyWT

  1. #1
    Stegodon
    Registered
    Mar 2009
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    127

    Default Engine Oil Question. Calling NinetyWT

    What are the practical differences between 5W20 and 5W30. All the paperwork for my engine makes it seem like the car will explode if I use the 30 instead of the 20. I mean, they make a point in stating how important the 20 is for my engine and for the thing to work properly. It's the Chrysler 5.7L engine with the thing that makes it only use 4 cylinders sometimes to save gas. I forget what it's called. Anyway, the paperwork that comes with the car says for that thing to funcion properly, the engine needs the 20, not the 30. It also recommends 30 for the smaller engine, but 20 for the big 5.7. Why? What's the deal?
    And the reason I'm asking is because I've heard of dealers--the official service guys-- in Australia using 5W30 because they can't get 20 there. Or something.

    And I just got back from my 200 dollar oil change.... yes, 200 fucking dollars. I'm doing it myself from now on!! Holy shit.
    Anyway, I just had my oil changed at an authorized service representative (a mercedes dealership). They used 5W30... and charged me like they used 5W24Karat.
    I think I should trust Germans when it comes to automobiles. But I also have the manual saying otherwise. What's the deal.

  2. #2
    Stegodon
    Registered
    Feb 2009
    Location
    Santa Fe, NM
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    259

    Default Re: Engine Oil Question. Calling NinetyWT

    I'm assuming you've got a Hemi with MDS (Multi-Displacement System).

    The first number in the 5W-20 designation is the cold (the W stands for winter) pumping temperature. This means its viscosity is similar to that of five weight SAE oil when you start your car. As your car warms up and the RPMs increase, the oil is going to be easier to pump. However, since different weight oils are rated at different temperatures, the polymers in a multi-grade oil will be more similar to that of a twenty weight oil when the engine reaches operating temperature (212F is used for these tests). In short, the difference between a 5W20 and 5W30 is negligible when it's cold, and the 5W20 is thinner at operating temp. If you were to use 5W30, it would be harder for the engine to circulate, and could cause problems, although you might be okay.

    It's important to note that SAE's rating system is a range, and not all 30 weight oils have exactly the same viscocity.

    FWIW, I've got the 5.7 in a Charger myself, and it's around $80 for an oil change. I use synthetic, though, and only change it every 10,000 miles.

  3. #3
    Stegodon
    Registered
    Mar 2009
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    127

    Default Re: Engine Oil Question. Calling NinetyWT

    Yea, that's exactly what I have. The Hemi with MDS. I just reached 6000 miles so I got my first oil change. Holy crap, I was not expecting the fee to be 150 EURO. It was synthetic, but geez! I will be changing the oil myself for now on. I will use 5W20 Mobile 1 and still pay less than 70 bucks with filter.
    The pamphlet says the MDS requires the 20wt oil. But I've read on message boards about Australian dealers using the 30, and now I just witnessed the German dealer do the same. I'm guessing it will be okay, but I am doing them myself for now on and using the right stuff.

    I hope it doesn't harm the MDS, but it's not like it ever kicks in anyway. I read that you have to be cruising at like 60mph for it to work. I am not often traveling that slow.

  4. #4
    Member
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    Mar 2009
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    50

    Default Re: Engine Oil Question. Calling NinetyWT

    On mine, they say MDS is only effective at 45 or less. It's apparently based off the engine RPMs and oil pressure, among other things. Presumably low RPM and low pressure means a light load and the engine can switch to four cylinders.

    Don't worry about 5w30 vs 5w20 - there's apparently a TSB from Chrysler approving the use of 5w30 in locations where 5w20 is not normally sold.

    I can't find a cite for the TSB, but I did find someone on another messageboard who says that the UK owners' manual calls for 5w30.

    Yet here in the UK the owners manual for my 5.7 Hemi states it is perfectly ok to use 5W30, due to unavailability of 5W20....
    (from here )

  5. #5
    Stegodon
    Registered
    Feb 2009
    Location
    Santa Fe, NM
    Posts
    259

    Default Re: Engine Oil Question. Calling NinetyWT

    Huh? Does it say that in your owners manual? I hear the MDS kick in all the time at 75 (but never more than 80); either that or it's going into overdrive and I'm mistaken. But there is definitely a very, very low rumble at around 40 mph, especially when I'm going up hill (which makes me think it's not the MDS that's causing that particular rumble. I read that there's a butterfly valve in the exhaust system to keep backpressure on the cylinders when they're only running on four.

  6. #6
    Elephant Myglaren's avatar
    Registered
    Apr 2009
    Location
    Washington, UK.
    Posts
    944

    Default Re: Engine Oil Question. Calling NinetyWT

    Different engine oil viscosities are applicable in different climates.
    Australia would likely have a higher one due to the predominantly higher ambient temperature there whereas northern Scandinavia would be more likely to need 0W20. or less.
    Lightly Seared On The Reality Grill

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