MDS, Chrysler’s Multi-Displacement System, shuts off four of the 5.7 Hemi’s eight cylinders under light load, such as steady highway cruising, to save fuel, and switches back to eight instantly when you need power. A non-MDS Hemi runs on all eight cylinders all the time. The hardware difference is in the valvetrain: MDS engines use special lifters on the cylinders that deactivate, plus oil control solenoids to switch them, and the engine computer must be set up for the system. Not every 5.7 Hemi has MDS; it appeared on many versions from 2005.
MDS vs non-MDS Hemi at a glance
| With MDS | Without MDS | |
|---|---|---|
| Cylinders running | Four or eight, switched automatically | Eight all the time |
| Lifters | Deactivating lifters on the switched cylinders | Conventional roller lifters |
| Extra hardware | MDS oil control solenoids | None |
| Fuel economy | Better at light-load cruising | Slightly lower at cruise |
| Oil sensitivity | Higher: the system depends on correct oil and pressure | Normal |
Do all 5.7 Hemis have MDS?
No. Many vehicles from 2005 on have it, but some years, models and configurations do not, which is why replacement engines are sold in both versions. Match the replacement to what your vehicle was built with, since the engine computer, wiring and calibration expect one or the other.
MDS lifters and the Hemi tick
Lifter wear is the most widely reported weak point of the 5.7 Hemi, and a failing lifter can damage its camshaft lobe. Owners often associate it with MDS engines, though lifter problems are not limited to them. Oil quality and change intervals matter on both. See 5.7 Hemi tick: causes and 5.7 Hemi problems.
Is MDS worth it?
For a truck that spends a lot of time cruising at steady speeds, MDS saves some fuel. For a truck that tows or works hard, it is active less often, and some owners prefer the simplicity of a non-MDS engine. If your vehicle came with MDS, the simplest path is to keep it working with the correct oil and regular changes.
Signs of an MDS problem
- A check engine light with MDS solenoid or cylinder deactivation codes.
- Ticking from the lifters, sometimes with a misfire on a deactivating cylinder.
- Rough running or a shudder when the system switches between four and eight cylinders.
- Fuel economy dropping because the system no longer activates.
Check the oil level and grade first, since the solenoids and lifters depend on oil pressure, then have the codes and solenoids tested; see low oil pressure.
Which replacement engine do you need?
The eighth character of your VIN identifies the engine. Send it to us with your year, make and model and we will confirm the right engine before you order.
- Dodge 5.7L V8 Hemi Engine 2005-2009 (with MDS): $4,899.00
- Dodge 5.7L V8 Hemi Engine 2005-2009 (Non MDS): $4,299.00
- Dodge 5.7L V8 Hemi Engine 2010-2012: $4,999.00
See 5.7 Hemi specs, how long a 5.7 Hemi lasts and 5.7 Hemi engines.
More guides: Eagle vs pre-Eagle 5.7 Hemi.
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