In another thread where someone was trying to get a recommendation on the options of 15w-40 HDEO to use in his volvo 850 (aluminum engine), lewk wrote: -------- "rotella has a harsher detergent(magnesium) than delo(calcium). this is something to consider if you have an aluminum block/head rather than cast iron.not sure how this would translate into wear but, milder is always a prime consideration if longevity is a factor." -------- I am curious to hear what people have to say about this. I have also heard a person or two mention a corrosion potential by using an oil that was too over based for the application, but would there be any such link with this? Thanks in advance.