OIL VISCOSITY
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From: AlABAMA
OIL VISCOSITY
Please dont shoot me. My manual says 15W-40. Mobil 1s site says10W-40. Amsoil says 5W-40. So whats a concerned 911 owner to do? All of these are good oils and I prefer AMSOIL but how do you determine which viscosity to go with. I know many like Brad Pitt but I believe the synthetics are better. So what oil and weights are you guys using. Yep yet another oil thread. OK Check the search function.
5th Gear
Joined: Mar 2013
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I was having a conversation with Kevin for UMW the other day , and he really has some info on this(perhaps hell chime in on this. My take on it1) get a " heavy duty tuxedo diesel truck" oil as they still are allowed to have more zinc in them( I think it's zinc)( if I'm wrong I'm sure someone will correct me) second consider synthetic, perhaps mobile one delvac 5 or 10 w 50, that's my two cents!
Instructor
Joined: Feb 2003
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From: Woodinville WA
Its the 40 that really matters, the number in front of the W is the viscosity when the oil is cold. All the oils you mention are the same viscosity once the engine has warmed up. Unless you are cold starting at temperatures below freezing, the difference between 5W, 10W or 15W is not important.
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Owner's Manual
The owner's manual on page 99 has two sets of columns.
The left set describes what weight to use if Mineral oil based engine oil is used.
I think this is where you are getting the 15W-40 from the owner's manual.
Then the right set of columns describes what weight to use if Synthetic oil based engine oil is used.
Since I drive my car all year round and it gets as cold as -10 or -20 in the winter and as warm as 90 in the summer, I chose 10W-40 Mobil1 synthetic.
The left set describes what weight to use if Mineral oil based engine oil is used.
I think this is where you are getting the 15W-40 from the owner's manual.
Then the right set of columns describes what weight to use if Synthetic oil based engine oil is used.
Since I drive my car all year round and it gets as cold as -10 or -20 in the winter and as warm as 90 in the summer, I chose 10W-40 Mobil1 synthetic.
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From: AlABAMA
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My thoughts: always use a synthetic oil. 15-50 is a good, year-around weight unless you are in freezing temps. Getting a bit more phosphorous and zinc for their anti-wear properties for our flat-tappet engines is a good idea. My recipe: I blend Mobil 1 15-50 and and Mobil V-twin 20-50 at about a 50% mix. The V-Twin has excellent anti-wear properties, and the 20-50 is close enough to the more ideal 15-50. IMHO.
Burning Brakes
Joined: Jul 2009
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From: Vista, CA
What exactly is a tuxedo diesel truck? Just kidding 
I use Shell Rotella T6. I also run it in my Turbo Diesel Volkswagens.
Bobistheoilguy.com is an interesting site worth flipping through if you are bored. Those guys do UOA (used oil analysis) religiously and have some interesting comments.
I use Shell Rotella T6. I also run it in my Turbo Diesel Volkswagens.
Bobistheoilguy.com is an interesting site worth flipping through if you are bored. Those guys do UOA (used oil analysis) religiously and have some interesting comments.