Longest run on Rotella T6 synthetic 5w40?

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Jan 12, 2008
Fellow oil guru's...I recentely ran a UOA (it is posted on the UOA forum under the name "ponch" ) on my 2007 duramax LBZ truck(modified with computer tuner), using rotella 15w40 CJ-4 dino oil for just over 9,000 miles this past summer which included heavy towing/driving this past summer.....to say the least the results were noting short of spectacular! NOW I am on a mission to run the rotella synthetic T6 5w40 for as long as possible to try and see just how long this oil will last in my pickup...the TBN of the UOA of the 15w40 triple protection after that run was at 7..in which blackstone labs commented back to me to try "11,000 miles next run on the same oil"...I am looking for fellow users of this T6 oil to guide me as to how long you think that I can safely stretch this interval? (without bypass filtration) I have learned VERY much from this website since I have been a member...and have been following the member's "dnewton" and "arkapig" on their results from running 10w30 HDEO's in their own duramax pickups (in year round temps) with great results! "Dnewton3" ran a UOA with 10w30 rotella dino with great results while "arkapig" ran a UOA of 10w30 delvac with also great results! I average no less than 25,000 miles per year...and am wondering if any of you think I could stretch this oil to this amount of miles WITHOUT bypass filtration? For this run I am currently using an Amsoil EAO oil filter which is good for the 25,000 mile/1 year mark... I want to justify the cost of using synthetics like this oil, (as I have learned that synthetics are a waste of money unless you greatly extend their use)...please chime in all! Thank you in advance!! -PONCH
Just run a UOA with TBN at 10K mi and then every 5K after that. Oil is done when TBN is about 30% of new or soot is over 4% (very unlikely) or enough fuel to lower 100C vis below 12.5 (possible) or thickened enough for vis >16 (very unlikely with synthetic). In 25K miles the Fe won't get anywhere near 1-200ppm. Incidentally you derive an advantage from the 5W40 that has to do with latitude, not miles: it does get cold in the winters in Michigan, and block heaters don't heat the oil pan. IMHO that alone is justification for using it. Charlie
I'd run it 15k with good filtration. Dmaxs are easy on oil. Have a few customers that run it out 30k with bypass filters with no problems and TBN still is solid
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