Heath - Question for you (and others).

Back in 2008, right at my second oil change, I swapped over to Amsoil. I have been running it in other vehicles for a LONG time, so I like the stuff a lot. Well, I went with the recommended 5W-20 and for some reason, my gas mileage went to hell right away. I called Amsoil and they told me to try 0W-20, so I did and my mileage came back up to what it was before + a slight improvement if I wasn't putting my foot down hard. Still an expensive oil change (two changes in two weeks), even as a preferred customer.

Fast forward to this weekend. I've been using 0W-20 and the EAO-42 filters. Got a buddy that told me he wouldn't recommend 0W-20, especially with a MDS engine (Engine Code 2). He said Amsoil doesn't recommend using anything other than 5W-20 in that engine and I told him he was wrong because I had the old printout from 2008 that showed 100% Synthetic 0w-20 Motor Oil first. Well.... I was wrong. I just checked the website. Amsoil has removed the 0W-20 recommendation as the primary oil, and now the site only lists 5W-20 for my truck and has a warning about the MDS needing to be run with 5W-20 only.

Recently, I started having some issues with my truck. At 40-45 mph, the truck gets "jerky", like the transmission is slipping, or the fuel is being starved from the engine. It's not showing any codes at all. At first, I thought it was the transmission. That has been checked and serviced. Still doing it. Got a full Hemi tune-up done at the dealership, including full cleaning of the fuel delivery system. Still doing it. I run Pi all the time - no difference with this issue. Then it hit me this week - I'm due for an oil change right now. I'm wondering if my oil being "due" for a change is causing the MDS system to slip in and out of 4/8. Hmmmm......

What do you think? Could be the reason for the issues? Should I go back to 5W-20, or keep using the 0W-20 that got me to 90K miles?

All the best,
Glenn

Interesting. Not owning a hemi myself..and not being a good reader, I was unaware of these engines having the MDS. What fasinates me more, or maybe interests is maybe a better word, is that oil viscosity apparently plays a part in how this system functions?
Not being a mechanic, I am in no way qualified to elaborate on the systme itself, but I might have an opioion or two on the oil situation. Here it goes.....

A 0/20 oil of course has a lighter viscosity at start up than a 5/20, but at operating temps, these oils are essentially operating at the same viscosity and the engine should not be able to tell the difference. Here are some figures:
The kinemitic viscosity of the 0 at 40C is 47cSt, the 5 is 50.
The kv at 100C is 8.7 and 8.8 respectively.
So as stated at full operating temp, these oils are the same. At start up and during warm up, there is a slight difference. What would amaze me is the the engine could sense this difference and that the MDS senses the "power needed or not needed" in this actual range. Talk about sensitive!!

Now back to your specific case. You mention you ran the 5/20 when you got it. Back then we did not have the 100% full syn 5/20 in the signature series. The 5/20 we had and still do is in the XL product line. So for any make or model that required a 5/20, AMSOIL listed either the XL 5/20 or the Sig. Series 0/20 for product options. Then about 6 months ago they came out with a 5/20 Sig Series and of course then changed the recommendation on the lookup guide to include this. What I don't know is when Dodge made the recommendation to use 5/20 only? Was this from the very beginning? What I afriad is that amsoil may have been comfortable recommending and backing their 0/20 previously and then when the 5/20 came out, conforming with what dodge recommended. I just don't know?
With that being said and you developing some issues with the 0/20 and the 5/20 available in sig series, I'd switch myself. Product is just as good and if it elimiates the problem...great.
I'm still amazed that the oil could make a difference in power detection. Question for anyone that has these. Do they essentially shut down on idle or will they shut down cruising at hwy speed or at any point while driving? If so, and oil does play a part, this may be another "test" that shows sythetic oil (in this case amsoil), does reduce frition in an engine and take less power to run...hence shutting down the mds at less than desirable times?

My hands are tired now. Hope I didnt' rambe too long. I'm very interested in this issue and may take it up with tech support to see if this has been a common issue or not.

Glenn, I think I mentioned it but yes I would switch to the 5/20 now that we have it in the sig series line.

Here is a overview that was done by Ram Tech am fellow member that is also a mopar tech.

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.

Isn't technology something...the more sofisticated they become, the more potential problems and harder they are to fix. Remeber the days when you could look under a hood and actually see the ground
I assume this is all for fuel economy? Does anyone know how much difference it make in mpg's?

Well... I took a chance on the new 5W-20 being right and placed an order just now. Wish me luck. I need it. Dodge Dealer doesn't seem to know what the problem is. No codes. No signs of anything broken. I'm at a loss for what is wrong, so I'm hoping this MDS issue might be it.

I don't know what others are getting for gas mileage, but I was getting 14 in the city for the longest time. 19 on the highway during long road trips. 12 if I was pulling my boat on those long road trips. Lately, I've been averaging 12 in the city, and it's been so long since I've taken my boat out, I have no idea what it's averaging while towing. My last long road trip averaged 15, so I'm definitely much lower than I was just a few years ago.

All the best,
Glenn

cajuntec said:

Still an expensive oil change (two changes in two weeks), even as a preferred customer.

Click to expand...

Never gave it any thought, maybe I should elaborate on the term preferred customer Glenn used, in case one was curious as to what it meant. You can find details here:
AMSOIL Preferred Customer Account

If it interests anyone, just click on the animated banner on the right side of the page.