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I run M1 0w-40 in my jeep SRT8 I was just curious if i can also run this in my 06 Hemi limted commander? Reason being it would keep things simple to buy the same oil in bulk for both. TIA
 

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I run Mobil 1 0W-30 in my 4.7 L. Maybe someone else with a HEMI can post up what they use for oil because I'm not 100% sure that all engines (3.7, 4.7 or HEMI) runs the same viscosity...I'd be curious to find out too.
 

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My 5.7L calls for 5w-20. I would not run 0w-40.... 0w-20? sure, but no way would i run a 40 weight.

I hear you about buying bulk... i used to need 5w-30 for my sierra and 5w-20 for the Commander... Since i traded in the Sierra for a Liberty (for the wife) buying oil is MUCH easier; a case of 12 quarts of 5w-20 takes care of both the vehicls- 7 for the Hemi and 5 for the 3.7.
 

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The O.M. specifically warns against using anything but 5W-20 oil for the Hemi, because of the MDS system that uses engine oil pressure to activate linkages in the valve train to de-activate 4 cylinders. Sounds like something that could be a very expensive experiment if it goes wrong.

They changed recommendations over the years in the O.M., so definitely check your MY O.M., because it may be different.

An SRT8 probably is equipped with the 6.1L HEMI, which did NOT have MDS, so using a different viscosity oil probably is NOT as bad as a 5.7L HEMI with MDS.

What happens with MDS if you use a different viscosity, I don't know, and I would NOT be surprised at all if you can't notice a difference. BUT, considering the stress the valve train is under and the MDS system only increases that stress, I also would NOT be surprised if using the wrong viscosity oil could create a different response in the system that results in excessive wear or increased chance of breakage.

So, I have to ask, the engineers that designed and spent thousands of hours testing the HEMI came up with a recommendation of what the best oil viscosity is to use, what have you come up with as the reason to use the viscosity that you use?

NOT that I'm that against doing something different than the manufacturers recommendation, if you have a good reason or good evidence to do otherwise, BUT, so often when I see people using an oil viscosity far different than recommended, there reason is nonsense, e.g. "I heard good things about this oil", "It's what I used in my other car and it worked well", "Ferraris use this viscosity oil", etc...

Yes, good quality Synthetic (there are a lot of pretenders that aren't as good out there) you can go to different viscosities and protect as well as the recommended viscosity. Yes, there are Racing Teams that make the conscience decision to use lighter viscosity oils for the gains in less pumping losses and rebuild the engine every season, so there are good reasons, as long as people know what they are getting into and actually measure the differences and figure out if they made a good decision or NOT.

What does your oil pressure gauge show for difference in oil pressures for different conditions when using the 0W-40 viscosity?
 

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I was going to say.... what's the recommended fluid for the SRT8? If it's also 5w-20, why run 0w-40??? If anything you'd think you'd want the "lighter weight" oil in there regardless.
 

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I was going to say.... what's the recommended fluid for the SRT8? If it's also 5w-20, why run 0w-40??? If anything you'd think you'd want the "lighter weight" oil in there regardless.
Yea, 0W-20 I can see, arguably using 5W-20 conventional oil, the viscosity has sheered down to 0W-20 before you change it and its NOT much of a difference anyway. Using synthetic, its probably still darn close to the original viscosity by the time you change it.

0W-40, I can see it being very possible to have big differences in oil pressure and circulation at higher temps and that might have a big effect on the MDS. As well, the wider spread in the viscosity, 40pts instead of 15pts, could that result in more shearing because of the need for more additives to get that viscosity spread? It may be different for synthetics, usually for conventional it is a very reall efffect of using larger viscosity spread oils, the extra additives to get there waters down the oil and you get more negatives that come from the additives. Usually the narrowest spread of viscosity (that meets your needs effectively) means more pure oil and better longevity and less additives that burn up in the oil and leave deposits and gunk.
 

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Some people have run the heavier weight oil in the MDS HEMI and all it does is prevent the MDS from kicking in. You will see your fuel economy drop, but not much else.
 

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From the 2006 Owner's Manual:

NOTE: Vehicles equipped with 5.7L engines must use
5W–20 oil. Failure to do so may result in improper
operation of the Multiple Displacement System (MDS).
Refer to “Multi Displacement System” in Section 5 of this
manual.
 

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I was going to say.... what's the recommended fluid for the SRT8? If it's also 5w-20, why run 0w-40??? If anything you'd think you'd want the "lighter weight" oil in there regardless.
Found this in a GC STR8 forum:

The owners manual, the cap on the oil fill tube and the SRT engineers say Mobil 1 0W-40
 

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Seems I got my answer too. 0W-30 in the 4.7 L. 0W-40 in the 6.1 L. & 5W-20 in the 5.7 L. & also 5W-20 in the V6. Kinda amazing that 4 engines use 3 types of oil...it is what it is I guess.
 

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The 6.1L HEMI may have a higher redline or something in the changes in design may created more stress the engineers decided it needed the higher viscosity when warm.

OR maybe, simply the 6.1L HEMI, not having MDS they decided 0W-40 Synthetic protected and performed best, and had to reduce the viscosity for the MDS in the 5.7L HEMI to get the MDS to work right. And since they did NOT want to limit the recommendation for the more common 5.7L to Synthetic only, they bumped up the cold temp to 5W from 0W, so they got a min level of protection if you used conventional.

Its pure speculation that could be totally wrong. What we do know, the engineers that designed and tested the 5.7L recommended 5W-20 oil, specifically so the MDS would work right and provide the best performance and protection to make the motor last. Unless you know more than the engineers, I would stick by the recommendation.

IMO, unless you have oil pressure gauge, you're foolish experimenting with oil viscosities. As well, unless you know for sure, I would NOT mess with that MDS system, that thing really impresses me as being capable of making a mess of the valvetrain, even the engine.
 

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Seems I got my answer too. 0W-30 in the 4.7 L. 0W-40 in the 6.1 L. & 5W-20 in the 5.7 L. & also 5W-20 in the V6. Kinda amazing that 4 engines use 3 types of oil...it is what it is I guess.
And it changed over the years also, I had a 2006 V6 owner correct me when I told him the O.M. recommends 5W-20 for the V6 and he used the wrong oil. He quoted the 2006 O.M. stating it needed a different viscosity than the later years. I think it was 5W-30.
 

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And it changed over the years also, I had a 2006 V6 owner correct me when I told him the O.M. recommends 5W-20 for the V6 and he used the wrong oil. He quoted the 2006 O.M. stating it needed a different viscosity than the later years. I think it was 5W-30.
I think it was 2008 when they started recommending 5W20 for all of the engines.
 

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IMO, unless you have oil pressure gauge, you're foolish experimenting with oil viscosities.
It's actually a bit more involved than just an oil pressure reading too. I dabbed a bit in bearing design (cycle life and lubrication). Depending on the clearances in the bearings and the RPM, a specific viscosity range is required to attain full lubrication. In a quick 20 second explanation of something that's a pretty detailed science; If the oil is too thick, the bearing won't draw in the oil required for lubrication. If the oil is too thin, the bearing won't lift the oil around its circumference for full lubrication.

Now, while i did bearing design, it was not for engines/crankshafts. But I have built engines and know that bearing clearance is one of the most important factors to ensure you have 100% correct.

Im not sure whether viscosity ranges of 20 to 40 weight oils are well within the "acceptable" range for full bearing lubrication or not. But i do know that the resolution for pumps "and oil pressure" is not fine tuned enough to determine if the bearings themselves are getting proper lubrication. I would just stick to what the manufacturer recommends.
 

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I think it was 2008 when they started recommending 5W20 for all of the engines.
Hmmmm, I wonder how much the Dealerships factored into that decision?

Either the Dealers pressuring corporate, so they can get more profit margin by bulk purchasing one oil, -OR- corporate did it to simplfy things, since too many dealerships proved so incompetent, they couldn't get the oil viscosity right during oil changes?
 

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From the 2008 Owner's Manual:

"Engine Oil Viscosity (3.7L/4.7L/5.7L Engines)
SAE 5W-20 engine oil is recommended for all operating
temperatures. This engine oil improves low temperature
starting and vehicle fuel economy. The engine oil filler
cap also shows the recommended engine oil viscosity for
your vehicle. For information on engine oil filler cap
location, refer to the “Engine Compartment” illustration
in this section."
 

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From the 2008 Owner's Manual:

"Engine Oil Viscosity (3.7L/4.7L/5.7L Engines)
SAE 5W-20 engine oil is recommended for all operating
temperatures. This engine oil improves low temperature
starting and vehicle fuel economy. The engine oil filler
cap also shows the recommended engine oil viscosity for
your vehicle. For information on engine oil filler cap
location, refer to the “Engine Compartment” illustration
in this section."
Does that viscosity recommendation apply only to '08 onwards or is it backwards compatible with the '06 4.7s?
 
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