Ferrari Forum - View Single Post - Best oil for 87 328 GTS located in Southern California

03-21-2006, 07:21 AM

A 5W-50 oil (even a full synthetic) will have to have a significant amount of viscosity improvers to meet the 5W-50 spec. It is these viscosity improvers that shear down under stress and you end up with an oil closer to 5W-40 (or even a 5W-35 oil). So if you want a xW-50 oil (for some reason) then start with a 15W-50 oil and it will not have as big a dose of viscosity improvers and will stay "in grade" longer.

For street driving and even agressive back road driving, I can recommend any of the 0W-30 and 5W-30 synthetics. If you have a temperature guage, and the oil temps never get above 250dF then a xW-30 oil has enough viscosity to do the job the engine needs done. It is only when you start seeing temperatures above 260dF that a xW-40 oil (and thinker stuff) comes into play.

Then there is that little issue of oil consumption. My F355 tends to consume a little xW-30 oil, so I stick with an xW-40 oil even when I run the snot out of the car on race tracks in the heat of Texas summers (think 105dF ambients). I tried a number of xW-50 oils and ended up running hoter track oil temperatures and had lower idle oil pressures comming off the track with the thicker oils. All in all, for my 355, the xW-40 oils seem to be working better.

I even ran an experiment with xW-30 oils in the hot Texas summer on race tracks. These oils had almost as good characteristics at the track as the xW-40 oils, the only real concern was the consumption rate. So, for this reason, I backed down to xW-40 oils.

I am currently running 5W-40 T&SUV Mobil 1 (which has been relabled as 5W-40 Turbo Diesel). This oil tends to the center of grade while most M1 oils tend towards the thin end of their respective grades. AMSoil and RedLine tend towards the thick end of their grades (or did last year).

With a careful wathc on the oil pressure guage, I can see that a day at the track will have caused some viscosity breakdown, so I change the oil just after a track day (or weekeknd) so that the engine is always well protected. A fresh batch of oil (full warmed up at 190dF) will read 80 PSI at almost any RPM above 2500. After a good hard track day, the oil pressure will decrease to 73-ish PSI under the same kinds of driving situations. In addition to shearing down, a day at the track will consume the anti-wear part of the oil protection package. So a fresh batch is in order.

All in all, I am a fan of using the thinnest oil that has sufficient viscosity at full operating temperature. For engines that don't see the hot side of 250dF, the xW-30 synthetics are just fine and will protect as well as the thicker oils, and may deliver a few ponys to the rear wheels due to lower pumping losses. Still I use xW-40 oils so the car is always track ready.

03-21-2006, 07:21 AM	#9 (permalink)
Mitch Alsup (Mitchalsup) Posts: n/a	A 5W-50 oil (even a full s A 5W-50 oil (even a full synthetic) will have to have a significant amount of viscosity improvers to meet the 5W-50 spec. It is these viscosity improvers that shear down under stress and you end up with an oil closer to 5W-40 (or even a 5W-35 oil). So if you want a xW-50 oil (for some reason) then start with a 15W-50 oil and it will not have as big a dose of viscosity improvers and will stay "in grade" longer. For street driving and even agressive back road driving, I can recommend any of the 0W-30 and 5W-30 synthetics. If you have a temperature guage, and the oil temps never get above 250dF then a xW-30 oil has enough viscosity to do the job the engine needs done. It is only when you start seeing temperatures above 260dF that a xW-40 oil (and thinker stuff) comes into play. Then there is that little issue of oil consumption. My F355 tends to consume a little xW-30 oil, so I stick with an xW-40 oil even when I run the snot out of the car on race tracks in the heat of Texas summers (think 105dF ambients). I tried a number of xW-50 oils and ended up running hoter track oil temperatures and had lower idle oil pressures comming off the track with the thicker oils. All in all, for my 355, the xW-40 oils seem to be working better. I even ran an experiment with xW-30 oils in the hot Texas summer on race tracks. These oils had almost as good characteristics at the track as the xW-40 oils, the only real concern was the consumption rate. So, for this reason, I backed down to xW-40 oils. I am currently running 5W-40 T&SUV Mobil 1 (which has been relabled as 5W-40 Turbo Diesel). This oil tends to the center of grade while most M1 oils tend towards the thin end of their respective grades. AMSoil and RedLine tend towards the thick end of their grades (or did last year). With a careful wathc on the oil pressure guage, I can see that a day at the track will have caused some viscosity breakdown, so I change the oil just after a track day (or weekeknd) so that the engine is always well protected. A fresh batch of oil (full warmed up at 190dF) will read 80 PSI at almost any RPM above 2500. After a good hard track day, the oil pressure will decrease to 73-ish PSI under the same kinds of driving situations. In addition to shearing down, a day at the track will consume the anti-wear part of the oil protection package. So a fresh batch is in order. All in all, I am a fan of using the thinnest oil that has sufficient viscosity at full operating temperature. For engines that don't see the hot side of 250dF, the xW-30 synthetics are just fine and will protect as well as the thicker oils, and may deliver a few ponys to the rear wheels due to lower pumping losses. Still I use xW-40 oils so the car is always track ready.