911SC motor oil
10-16-2002, 07:14 PM
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911SC motor oil
I have an 81 911SC. Engine needs an oil change. Can I use synthetic (Mobil 1 15-50)? I have read that an engine that is fed petroleum based oil and then switched to synthetic may leak or cause some type of bearing damage. Is there any truth to this, or am I reading the wrong information from the wrong people?!
10-16-2002, 08:27 PM
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Sanchez,
These concerns cropped up when synthetics first started being used, although I haven't heard about bearings going before. Generally, movement to synthetics in any 1978-on Porsche engine should be OK without any leakage. I changed to Mobil 1 15W50 in my 81SC at around the 100K miles mark, and didn't have any leakage.
Here's some more information from the 964 FAQ:
In June 2001, Porsche updated their oil recommendations for all 4, 6, and 8 cylinder models, from 1973 to current. They are:
Castrol/Syntec 5W-50
Mobil 1 0W-40, 5W-40
Sun Oil/Sunoco Synturo Gold 5W-40
Texaco/Havoline Formula 3 Synthetic 5W-40
Valvoline/High Performance Synthetic 5W-30
Viscosities recommended for the Turbo are 0W-40, 5W-40 and 5W-50.
In that same update, Porsche reduced the outside temps that the various viscosities should be used in. xW-30 oils are now for use up to outside temps of 85 degrees F. For outside temperatures of 85 degrees F and above, the second number in the oil rating should 40 or greater. Most drivers who take their Porsches on the track use an xW-50 oil, like Mobil 1 15W-50.
These concerns cropped up when synthetics first started being used, although I haven't heard about bearings going before. Generally, movement to synthetics in any 1978-on Porsche engine should be OK without any leakage. I changed to Mobil 1 15W50 in my 81SC at around the 100K miles mark, and didn't have any leakage.
Here's some more information from the 964 FAQ:
In June 2001, Porsche updated their oil recommendations for all 4, 6, and 8 cylinder models, from 1973 to current. They are:
Castrol/Syntec 5W-50
Mobil 1 0W-40, 5W-40
Sun Oil/Sunoco Synturo Gold 5W-40
Texaco/Havoline Formula 3 Synthetic 5W-40
Valvoline/High Performance Synthetic 5W-30
Viscosities recommended for the Turbo are 0W-40, 5W-40 and 5W-50.
In that same update, Porsche reduced the outside temps that the various viscosities should be used in. xW-30 oils are now for use up to outside temps of 85 degrees F. For outside temperatures of 85 degrees F and above, the second number in the oil rating should 40 or greater. Most drivers who take their Porsches on the track use an xW-50 oil, like Mobil 1 15W-50.
10-17-2002, 12:04 AM
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I switched from Valvoline Racing 20/50 to Redline 20/50 at 150,000.I now have 244,000 on my 83SC.One very small leak which has come up in the last 50,000 miles, but I have 244,000 miles on an origional motor, upper engine at 111,000 miles and that is it ! I'll be rebuilding around 275,000 or 300,000.I get really great milage and have dyno'd the car last year with 183hp at the rear wheels.I feel the synthetic gave me a couple of extra horses !
