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Discussion Starter #1
I've been running 0w20 synthetic this winter and am preparing for another oil change. I realize I can continue to run this weight all summer long without having to go back to 5w20 like the manual says, but I was wondering if I would screw up my MDS if I ran a xW30 oil instead? It would be fully synthetic of course.
 

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Discussion Starter #3
I run 5W-30 in summer only wth no codes and much improvment in oil pressure and mds still functional .
What do you run in the winter? And did you notice an increase in fuel consumption with your "30" weight oil? I'm assuming it's synthetic.
 

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There is no difference in the cost between 5w30 or 5w20 so risking the MDS not working is not really worth it is it?

Synthetic 5w20 or 5w30 is $18.99 for a 4.4L jug for either grade.
 

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There is no difference in the cost between 5w30 or 5w20 so risking the MDS not working is not really worth it is it?

Synthetic 5w20 or 5w30 is $18.99 for a 4.4L jug for either grade.
i second that,
go with what it says on the cap, you probably wont cause any damage right away but down the road you never know. I have a buddy who never gave a **** and threw whatever into his civic, including different types (ie mixing 10w30 with say 5w30, which i know is NOT what your doing), his car has run fine for over 100 000 kms like that but now hes starting to feel the pain of his lack of care.
 

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i second that,
go with what it says on the cap, you probably wont cause any damage right away but down the road you never know. I have a buddy who never gave a **** and threw whatever into his civic, including different types (ie mixing 10w30 with say 5w30, which i know is NOT what your doing), his car has run fine for over 100 000 kms like that but now hes starting to feel the pain of his lack of care.
To be honest, your friend shouldn't be having any issues with mixing 5w30 and 10w30 seeing they are the same weight.
 

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Discussion Starter #7
There is no difference in the cost between 5w30 or 5w20 so risking the MDS not working is not really worth it is it?

Synthetic 5w20 or 5w30 is $18.99 for a 4.4L jug for either grade.
i second that,
go with what it says on the cap, you probably wont cause any damage right away but down the road you never know. I have a buddy who never gave a **** and threw whatever into his civic, including different types (ie mixing 10w30 with say 5w30, which i know is NOT what your doing), his car has run fine for over 100 000 kms like that but now hes starting to feel the pain of his lack of care.
Thanks guys, but it is (and never has been) a question of dollars. I suspect the 5w20 was only mandated because of C.A.F.E. standards, as it is more fuel efficient than a 5w30 and even though it's a small percentage, once multiplied by the number of vehicles Chrysler sells, you can see how they would ask for that weight to be "spec".
My concern is that the car now has 135 000 kms and is driven 90% on the highway. Wouldn't a "w30" synthetic offer better protection than the w20? The MDS becomes a concern because the car is on cruise control the entire way between Montreal and T.O., so I would need it to continue to function. This is only about what would better protect the engine and it's parts, given the conditions I drive it in and the mileage on it now.
 

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I run Mobil 1 5-30 ,no change in gas mileage but improvement in oil pressure Hot idle 219f when fans turn to high, oil temps 230f ,oil pressure down to 15 lbs with 5-20 , with 5-30 i get 22 lbs oil pressure . All other seasons i use 5-20 as oil temp and engine temps are lower so oil pressure is in the same 22 lb range. The 6.1 gets 0-40 and 15-40 if you have the piston skirt noise. Although there is no mds these oil weights provide lots more oil pressure and protection for a high performance motor than the 5.7 with mds gets. I used to build motors with high volume 90LBS oil pumps and always watched my guages. So i dont go over 5-30 weight with MDS but watching guages i get better pressure with it.
 

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Thanks guys, but it is (and never has been) a question of dollars. I suspect the 5w20 was only mandated because of C.A.F.E. standards, as it is more fuel efficient than a 5w30 and even though it's a small percentage, once multiplied by the number of vehicles Chrysler sells, you can see how they would ask for that weight to be "spec".
My concern is that the car now has 135 000 kms and is driven 90% on the highway. Wouldn't a "w30" synthetic offer better protection than the w20? The MDS becomes a concern because the car is on cruise control the entire way between Montreal and T.O., so I would need it to continue to function. This is only about what would better protect the engine and it's parts, given the conditions I drive it in and the mileage on it now.
No, there is no better protection offered at all. In fact, I have seen people put a w20 in an engine designed for a w30 and actually saw their wear numbers decrease substantially through oil analysis.

Thick is not better. Flow is paramount the faster you get the oil where it should be the better.
 

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Discussion Starter #10
No, there is no better protection offered at all. In fact, I have seen people put a w20 in an engine designed for a w30 and actually saw their wear numbers decrease substantially through oil analysis.

Thick is not better. Flow is paramount the faster you get the oil where it should be the better.
That being said, I can then run the 0w20 I have in it now year round?
 

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That being said, I can then run the 0w20 I have in it now year round?
You bet! Remember, the 0 in 0w20 is not a weight, it is a cold flow number relating it to a viscosity at low temperature. In fact, I would run 0w20 if I could here but it is hard to find in my local stores so I run a synthetic 5w20.

Here is a chart that will explain it:

 

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I run Mobil 1 5-30 ,no change in gas mileage but improvement in oil pressure Hot idle 219f when fans turn to high, oil temps 230f ,oil pressure down to 15 lbs with 5-20 , with 5-30 i get 22 lbs oil pressure . All other seasons i use 5-20 as oil temp and engine temps are lower so oil pressure is in the same 22 lb range. The 6.1 gets 0-40 and 15-40 if you have the piston skirt noise. Although there is no mds these oil weights provide lots more oil pressure and protection for a high performance motor than the 5.7 with mds gets. I used to build motors with high volume 90LBS oil pumps and always watched my guages. So i dont go over 5-30 weight with MDS but watching guages i get better pressure with it.
Actually, you are affecting your fuel ecnomy seeing the MDS is related to oil pressure and the lower the oil pressure, the more apt the MDS is going to activate and stay activated.

The 7lbs of pressure is quite a difference and will have the MDS thinking you have a higher engine load than what you actually have so it will kick out of MDS much easier.

There is a complete TSB about this and the oil weight is not for CAFE, it is indeed for the MDS system seeing it in part is actualted by the oil pressure.:fing02:

There is no benefit in running a 30 weight in an MDS HEMI whatsoever.
 

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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.... My MDS works just fine, no issues. The only thing that causes the oil weight to interfere with MDS operation is the leak-down rate of the oil from the hydraulic lifters when MDS is activated, it is nothing to do with pressure. The ecu gets an oil temp input, and part of the algorithms for MDS activation is <oil temp above xxx>. This is purely to prevent the MDS system activating when the oil is cold and thick, and partially opening the valves on those cylinders due to lack of bleed-down, as this would cause rough running and slight imbalance as you loose the "air-spring" effect on those 4 cylinders.
 
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