(quoted from post at 13:34:57 03/20/11) Some say this is always an argument,well that's mostly because a bunch of them don't know what they are talking about or are stuck in the past.There is nothing wrong with Shell Rotella 15/40.Now the people who say that straight 30 weight is better aren't telling the truth.However,an engine that has been using straight 30 weight,you should probably continue to use the same brand straight 30 weight because I have seen an engine leak oil out of the front or back main from switching to 15/40.That doesn't mean 30 weight is better,it just means it will stay in old type seals better.Most stuff made from the late 1970s should have a newer type seal that will work with 15/40 especially if its been rebuilt and new crank seals were put in.15/40 gives better protection to your bearings over a wider temperature range.Its basically the same oil,its a different additive package to make it multigrade.I dont know about other oils,but as long as they have the same additives as Rotella the other 15/40 oil is good.Kendall is another 15/40 thats good.Interstate is good.Just has to be like Rotella.
Now I have rebuilt lots of diesel engines.Back in the early 1980s when I started working on diesels they used 30 weight or series 3 oil for diesels.We rubuilt Detroit engines at around 100,000 miles.Cummins engines might run a little farther,but at about 80,000 miles you had to put main and rod bearing in usually.Once they started using 15/40 you could run them a lot farther.We started off changing bearings at about 150,000 miles,then we went to 300,000 miles and then we just would pull one and see what it looked like,if it looked good and still had good oil pressure probably wouldnt change them unless we needed to work on the engine.By the time I started doing another job around 1988,they had engines that had ran up to a million miles and had never had a wrench on it anywhere.That was Shell Rotellas advertisement.They had pictures of pistons they took out of a diesel engine with a million miles on it.Ive worked on engines that had over 500,000 miles on them before they needed anything.
Just like anything else,if you keep oil in it,it will last a lot longer.What I have seen 15/40 oil do is make engines last a good 3 times longer,and burn less oil in that period of time than any engines on series 3 ever did that I worked on.Plus the bearings looked better at 300,000 miles than series 3 bearings looked at 100,000 miles.
You still probably should change bearings at about 500,000 miles,just to be safe,but you will maybe look at them and wonder why you are doing it if they always kept Rotella oil,or any other 15/40 that has additives like Rotella in it,but then they might be showing copper too,so its a good idea to swap them I think.
Also where I worked at they had bulk oil.They got a good deal on a barrel of Cummins Blue 15/40 and we ran that.Some of the trucks burned 2 or 3 gallons a week on the Cummins Blue and they switched to Rotella and some of the trucks that were burning 2 or 3 gallons a week went down to a gallon a week.I dont know why,but I saw it myself.
I'm not going to say that Shell Rotella is the best oil,but if there is any better oil,it has to be real good oil.
