I'm a new owner and have recently read thorugh a bunch of threads on this site. Looking through the records on my car I see that over the years its had 5-40, 15-40, 20-50, dino, synthetic, dino again, synthetic, 'racing oil', all sorts of stuff. I also have some other older cars and motorcycles and have gone through this discussion before- my 911 uses BP 20-50. So, after all of that 'research' I'm using Shell Rotella T6 synthetic 5-40 without any more worry.
I used Mobil 1 15W-50 and was very satisfied with it and had a lot of peace of mind about its capabilities. The sting of buying 19 quarts, typically at $8.99/qt, was reduced by watching Walmart ads for 5 quart jugs at $25 each. Just don't tell anyone that you buy the oil for your Ferrari at Walmart!
Last year I began using Amzoil 20/50 containing the proper zinc content. The results were immediate... the tappets lubed up so quickly, that they went silent in less than 30 seconds and hums like a Singer sewing machine. I have yet to see the oil temp over 212f, which is exactly where manufacturers prefer engines to run. Also, upon total rebuild of the T400 tranny,I began running Amzoil ATF. with outstanding results..It costs about the same as other brands, but, "Frankly Scarlett..I don't give a damn". Baldwin oil filters. Jq.
concerning water temp/vs oil temp: My 400i GT tracks almost exactly 80-90C water, and 90 to 100C oil. Consistently 10 to 15 deg C above water temp. Using 15W-50 Mobil 1, recently changed to Castrol 0W-30 SPT. Ed Trottier Aiken, SC
This is what I use as well with the same results. I've used Castrol and Royal Purple but I like the Amsoil Z-rod 20W-50. Don't forget the new crush-washer on the drain plug. Image Unavailable, Please Login