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i changed the oil in my 300c and put royal purple 10w30, i know that the recommended brand is 10w20, will this damage my engine? should i drain it and put the correct oil? how long can i go with this oil?
 

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It won't damage your engine but the MDS solenoids are made for lighter oil so your engine may not switch to the 4 cylinder mode. Other than that it's probably good for the engine.
 

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On the 2005 and 2006 there is no indicator. When you are on a straight level road the engine will make a droaning sound in the 4 cylinder mode around 50 mph or you can watch you average mileage start to climb above 50 mph on a level road. You should get 28 mpg or more at 50-55 mph. If you only get 21-22 mpg the heavy oil has locked it out.....
 

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The Multi Displacement System selectively deactivates cylinders 1,4,6 and 7 to improve fuel economy. It has two modes of operation:
- 8 cylinders for acceleration and heavy loads
- 4 cylinders for cruising and city traffic

The main components of the MDS are:
- Unique MDS camshaft
- Deactivating roller tappets
- 4 control valve/solenoids
-control valve/solenoid wiring harness
- oil temp sensor

OPERATION
Cylinder Deactivation:

Trap an exhaust charge
Normal combustion event
Don't open exhaust valve
Don't open intake valve
Piston is an air spring
Cylinders deactivated in firing sequence

Cylinder Reactivation:

Empty the cylinder
Open exhaust valve
Open intake valve
Normal combustion event
Cylinders reactivated in firing sequence


It has the following detectable issues:
-Solenoid circuit
-Failure to deactivate a cylinder(s)
-Failure to reactivate a cylinder(s)
-LOW oil pressure

If it doesn't activate/deactivate, it could be: a) low oil pressure; b) bad oil temp sensor; c) malfunctioning solenoid; or d) malfunctioning tappet.

Basically, you've put in a thicker oil, so low oil pressure won't be an issue. I run 0w30 synthetic in mine, and the "0" is only due to winter driving up here. The "30" between yours and mine is the same, and my MDS works fine. I don't think you'll have any trouble with it. You may have a hard time circulating the oil when the temperature drops to below -10 celsius (about 14 farenheit) which will result in accelerated engine wear.

Oh, and BTW, the manuals call for 5w20, not 10w20 as you said. You could use 0w20 or 5w20 (if you want to stay with the manual), or move up to 0w30 or 5w30 synthetic (which has better flow characteristics over conventional dino oil.......please ChuckKent......don't get that argument started again!.........). 10w30 is just a heavier weight (re: higher viscocity) at cold temps, hence the accelerated engine wear at cold temperatures.
 

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none

there is no argument.

5w-20 is the recommended oil. The reason is to allow for best operation of the MDS system.

Using a heavier oil does nothing but add drag and cost fuel, in addition to affecting the MDS. It will not harm the engine at all, but why would you want to disable one of the nicest features of a stock 5.7?
 

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Royal Purple is one of the best synthetic oils on the market, but it's not the cheapest. For the cost of the oil you should definitely get the 5W20.
 

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Do not use anything but the 5W20!
 

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So, in all, would you guys go full Synthetic on your 5.7's, like Royal Purple Street Synthetic Motor Oil - SAE 5w20 - Do you think that would be one of the best choices for the 5.7?

Amazon has cases of Royal Purple listed at $72 a case of 12 - $6 per quart!
 

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2Yutes,

There are alot of choices when it comes to full synthetic. The majority of forum members either use Mobil 1, Royal Purple, or Amsoil. Personally, I use Royal Purple 5W20 with a K&N Oil Filter.
 

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Yes I was looking at Royal Purple at Autozone and it was almost $8 quart. Good oil but too rich for me! 0w30 sounds interesting to me because I think the V-8 engine needs it long haul, but I understand the MDS limitation. I don't want to give up my excellent mpg by using a little heaver oil.....
 

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My next oil change will be to the new 0-20W Mobil 1. Its suppose to be their low friction oil to improve fuel economy. I put the 0-30W in my truck and it seems to like it.
I have used the RP 5-20W and it seemed to be quite good...Hemi seem to be quiet at idle. Didn't notice any fuel economy difference from Mobil 1 5-20W, so I've just been using Mobil 1 and buying it when its on sale at Wally World.
 

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I just picked up a case of Royal Purple 5W 20 and a Napa Gold filter for my next oil change....was one expensive oil change....
 
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