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Discussion Starter #1
Hope this thread doesn't get into a synthetic vs a dino oil thread.

I have a simple question about the SAE ratings for synthetic vs dino oil . I observe that generally the synthetic oils have lower SAE ratings (e.g. 5W40) instead of the dino (e.g. 20w50).

I have been using the BMW OEM motor oil 20w50 till now. I have 30K on my LT and I am considering switching from dino to synthetic. I have existing oil for my truck that's rated at 5w40. Is it ok to switch to a synthetic that has slightly lower ratings than the dino?
 

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The lower number is the oil's cold viscosity behaviour, basically an indication of its pumpability when cold, among other properties. W stands for winter. The higher number is the viscosity number which represents the oils behaviour at high temperature, the standard being 220 degrees F (from memory). Synthetics are basically able to be engineered to have a wider temperature/performance range than mineral products, this is partly because of the molecules being more uniform in size, and many other complex reasons. If you are really interested in understanding this I suggest you google it, there's heaps written about it, just wade through the info and take in what's of interest to you.
 

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I had the same questions recently, and wound up using the standard 20w-50 again, but found out you need to watch the other rating info too... my last post on it
 

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Not Approved: The API specification SJ is not approved for use in any BMW motorcycle. This latest API classification does not guaranty the required levels of wear protective additives such as Calcium, Magnesium, Zinc, etc. as with most prior API specifications."


Maybe just adding a one-a-day vitamin might do it? :rotf:
 

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LTFan said:
Hope this thread doesn't get into a synthetic vs a dino oil thread.

I have a simple question about the SAE ratings for synthetic vs dino oil . I observe that generally the synthetic oils have lower SAE ratings (e.g. 5W40) instead of the dino (e.g. 20w50).

I have been using the BMW OEM motor oil 20w50 till now. I have 30K on my LT and I am considering switching from dino to synthetic. I have existing oil for my truck that's rated at 5w40. Is it ok to switch to a synthetic that has slightly lower ratings than the dino?
Yes switch between dino and synthetic as many times as you want. They are really not that different, so they are intermixable . Just use the recommended viscosity.
 

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Discussion Starter #6
Got it. So I should find a synthetic that has similar ratings as the regular oil. I found a 15W50 in the BMW dealership today. I will use that.

Also found this Link the earlier post by CWS that was very helpful.
 
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