1sttruck

Again I notice that the engine is quieter with an oil change, this time going from Delvac 1300 to an Exxon XD3 Synthetic Blend. The stuff is kind of exotic as it's not easy to find, and it also stinks a bit when I shut the egine down. I'll fix the air intakes per other threads. I'm using a 3750 mile oil change interval as I have a CARB engine, and noticed that the noise seemed to pick up around 3000 miles. Based upon Dodge/Cummins recommendations for using 7500 mile oil change intervals in non-CARB engines I wonder what it is that makes for the quieter engine in fresh oil, and why it doesn't last up thru the suggested oil change interval.

ck1

funny...I mentioned that in a post last month and I was told that I was smokin sumthin or there is something wrong with my truck or ?....mine does the same thing and I also have a smogged up cali motor...there has to be somthing that is causing this...my oil gets diluted within 2000 to 2500 miles with the exception of this last trip to texas (my post was asking if anyone ever had their CTD changed at a truck stop and are they pick up truck friendly never did get a good answer and was told to have Wally world change it!! NOT))...I use Rotella all the time as I dont NEED synthetic as I feel that they are way overated oils for the price (ok amsoil lovers flame me!)...i was pondering changing the oil during this trip as I had 2 k on the change prior to my leaving california...I instead just dumped the oil and left the filter (i only had one left and couldnt wait for genos to send me my new case) and I have to tell you it is smoother and quieter than normal but is thinner then when fresh... My Jetta does the same thing and I use DELO 400 In that as I have since it was new...the jetta does have a EGR so I would think that would be the culprit but I believe my Cummins does not....so....any thoughts on OUR situations? could it be the fuel?...

mymaur

I've noticed it as well, just using Dino oil. On my older trucks, 1st gen, they will smoke a little less during the first few miles, after an oil change.

rossn2

CK1,

I didn't say to have Wally World change your oil...I offered that they could do it if you couldn't find a Truck stop along the way, and were in a pinch. I change my own and take the old stuff to be recycled at Wally World.

My, Non-calif engine and changed over at 7200 miles to synthetic (ok, yes Amsoil) and will run up to 15k or 6 months, whichever comes first, without using oil analyis. And, got to change oil filter at 7000-75k too...

You could easily go to 7500 miles within 6 months too (3750 x2) on a quality synthetic...

Redline says 10-12000 on their oil without oil analysis...

Just a thought...not pushing either way...

1sttruck

Looking at oil properties 'shear stability' seems to be a likely candidate for what makes for a quieter engine with fresh oil.

mymaur

This is the best explanation I've heard. Makes good sense.

1sttruck

I haven't been able to find a comparison of test results of shear stability, but have run across a few more comments about different engine noises decreasing with fresh oil. Single viscosity oils won't experience the decrease in shear stability like multi-viscosity oils will as it's the breakdown of the complex compounds used to create a multi-viscosity oil that result in a decrease in shear stability. Synthetics will also do better than dino oil in shear stability.

I find 100% synthetic oil too expensive for my use as I won't attempt extended drain intervals, but based upon my experience with Exxon XD 3 synthetic blend to date I will continue to use a blend.