What are you using ?

DUSTERDOWNS said
When i had my 340 built by a guy that builds pulling motors i asked if i could use shell rotella 15/40 as my oil. He stated that i could not only use it as a break in oil but continue to use it as a everyday oil . It has zinc and all the other things that a motor needs . I know after 43 years of trucking all the big truck engine builders use it and they all can't be that wrong. Just my opinion that's my oil and i'm sticking with it.
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The problem with diesel oil is that it is formulated for low RPM engines(diesel). We have seen on the dyno that at higher RPMs(over 6000) the oil starts to foam and that is no good. Now from using 10w 30 to 25w 50 there is a lose of horsepower of about 3 to 5 hp but the motors that use the 10w 30 need alot more work at freshen up time than the motors that ran the 25w 50.