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Hello all,


Just ordered my outfit about 2 weeks ago. Having never owned a diesel before you guys and this site are really schooling me on the truck before I even turn the key. Being a mechanic and service manager for about 12 years (retired from that many years ago and currently in new car sales), I am very maintenance orriented. I have run Mobil 1 in all my engines for about 15 years now and love the product. My basic question is this: the duramax diesel website, in their FAQ section recommends 15w40 weight oil and of course the proper API rating. Am I correct in stating that the Mobil Delvac1 is the synthetic oil for diesels (Mobil product) and secondary I see the only weight it comes in is 5w40. I notice alot of folks running this oil with no problems but there is alot of difference between 5w and 15w. I also see alot of folks running the Shell synthetic (Rotella is it?? ...I'm not familiar with Shell products) and this is 15w oil. Would that be better?? I live in Northern Virginia and it sometimes gets into the low single digits here in winter. Based on that, I guess I would have a problem running 15w in the winter and I don't like switching grades as the norm. Some further schooling please. Thanks much.


Joe
 

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You are on the right track.


Welcome!


15W40 is the diesel equivalant of 10w30 for gassers.


Delvac1 5W40 will be fine. the "5W" in the cold oil equivalancy. The Oil analysis guys will jump in here and correct me.


Shell rotella comes in dino and synth versions.


Personally, I use Delvac 1300 dino oil (15W40) and will shift to Delvac 1 @ 10,000 miles. I've run it through the winter and have had no problems. Oil pressure is a little higher than I like in cold but in a year it won't matter.
 

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GM says run 5wt BELOW zero. I tried 5wt and my oil pressure dropped a huge amount. My hot idle oil pressure was 14LBS. Way to low for me. Hot idle at 15wt dino oil was 30+ in my truck.

Im sure people here will flame me for posting this. Just watch your oil pressure if you switch it.
 
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