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Discussion Starter · #1 ·
I currently have a 3rd gen 08 dodge ram 5.7L that has MDS with 104,000 miles. I'm not exactly sure how the v8 to v6 cylinder change is actually healthy for your motor. My question is- If your inactive pistons aren't getting oil on the highway(in v6 mode) for some time and get dry, then when they go active again (v8) once it switches back, aren't you ruining your pistons? Isn't that horrible for your motor and after awhile the wear will cause you to need a rebuild? I understand people will say to make sure you use synthetic and the right oil at all times, but right now my fathers 07 5.3 chevy tahoe(60,000 miles) has the same thing and he is currently facing a motor rebuild for the same reason. And the dealer knows it's a problem but you haven't heard anything about it. But there is now talk of a big lawsuit. AND I know ford and dodge have this same economy mode that all act similar to each other. Is the MDS going to be a long term issue on my Ram, and should I get a tuner in order to hopefully avoid a motor rebuild myself as well? I've done some research on a couple different vehicles that have the v8 to v6 switch and it seems that once you start burning oil it's over. Could this just be a GM and Ford issue or should I really be looking to make sure I can avoid the same problem?
 

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First off, it's shuts 4 cylinders off....not 2.

and i don't think it works like what you think.

From another post. Or google "how mds works"

The Multiple Displacement System (MDS) provides cylinder deactivation during steady speed, low acceleration and shallow grade climbing conditions to increase fuel economy. Both four and eight cylinder configurations have even firing intervals providesmooth operation. Two cylinders on each bank are active when the engine is in four-cylinder mode – every other cylinder in the firing order. All of the cylinders that are deactivated have unique hydraulic valve lifters that collapse when deactivated to prevent the valves from opening. Engine oil pressure is used to activate and deactivate the valves. It is delivered through special oil passages drilled into the cylinder block. Solenoid valves control the flow. When activated, pressurized oil pushes a latching pin on each valve lifter, which then becomes a “lost motion” link. Its base follows the camshaft, but its top remains stationary, held in place against the pushrod by light spring pressure but unable to move because of the much higher force of the valve spring.

NOTE: It is critical to use the recommended oil viscosity in 5.7L engines that use MDS.

Deactivation occurs during the compression stroke of each cylinder, after air and fuel enter the cylinder. Ignition then occurs, but the combustion products remain trapped in the cylinder under high pressure, because the valves no longer open. No air enters or leaves. During subsequent piston strokes, this high-pressure gas is repeatedly compressed and expanded like an air spring, but fuel is not injected.
 

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I currently have a 3rd gen 08 dodge ram 5.7L that has MDS with 104,000 miles. I'm not exactly sure how the v8 to v6 cylinder change is actually healthy for your motor. My question is- If your inactive pistons aren't getting oil on the highway(in v6 mode) for some time and get dry, then when they go active again (v8) once it switches back, aren't you ruining your pistons? Isn't that horrible for your motor and after awhile the wear will cause you to need a rebuild? I understand people will say to make sure you use synthetic and the right oil at all times, but right now my fathers 07 5.3 chevy tahoe(60,000 miles) has the same thing and he is currently facing a motor rebuild for the same reason. And the dealer knows it's a problem but you haven't heard anything about it. But there is now talk of a big lawsuit. AND I know ford and dodge have this same economy mode that all act similar to each other. Is the MDS going to be a long term issue on my Ram, and should I get a tuner in order to hopefully avoid a motor rebuild myself as well? I've done some research on a couple different vehicles that have the v8 to v6 switch and it seems that once you start burning oil it's over. Could this just be a GM and Ford issue or should I really be looking to make sure I can avoid the same problem?
1. Goes 8 to 4
2. Pistons always get oil, it's the lifters that don't pump up
3. It's a chevy....
 

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I agree with the points above and also..

Your truck has over 100k miles and it has been using this system since mile 1. If you ask me the only problems you will not face is due to age or lack of maintenance not because of engine design.

I have seen thoee Hemi engines and older ones climb into the 200k range before I lost track of them.

My 2009 Hemi has 71k on it now with zero problems. The MDS system works just fine.
 

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Discussion Starter · #5 ·
Okay thanks for the education. One more question, I recently have been noticing that my oil pressure gauge is acting strange. When I'm on the gas -it's between high and mid pressure (im not sure what that is in number because my gauge doesn't read it) And then when I come to a stop sign or light and come to an idle or almost a stop - the pressure drops to in between Low and the Middle. If that doesn't make sense i can take a picture. It seems like it drops way toooooooo much and that scares me because it's been taking 1qt of oil in 3,000 miles. I've been told it's normal for it the pressure to drop that low and I've also been told I better hop over to a garage quick to make sure my oil pump isn't about to take a dump. Please reply thanks
 
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