Originally Posted By: Quattro Pete
Right, but does an actual Ferrari spec exist, and if so, what are the requirements?
The original Ferrari F355 spec oil (Shell Helix) has 14 cSt of operating viscosity (a medium thick 40 weight) and an HTHS of 4.2 cP, and unless you are driving this car below zero, it really does not matter a lot what thee xxW- number happens to be.
If you are going to run the snot out of the engine (safely and legally) it is the HTHS number you should be choosing. You can also use the oil temperature gauge to tell you whether the oil you have chosen is acceptable. If you drive and the oil temperature never gets over 250ºF, then any xxW-40 oil will be acceptable. as you get to 275ºF you need that 4.2 HTHS. If you get over 275ºF, you need a xxW-50 oil with an HTHS number in the high 4s or low 5s.
It should be pointed out that the F355 engine has direct valve actuation (no rollers in the valve system. A new (or heavily rebuilt F355 engine) should have at least 1200 ppm of lithium (ZDDP) and if you intend racing the car, the oil you arrive on track with should have 1400 ppm.
M1 TDT USED to have 1100 ppm but apparently this has dropped out of the required amount; TDT used to have a HTHS number of 4.2 also.
I did a quick check and had a hard time finding any oils that have HTHA equal to or above 4.2 cP and a 40 weight operating viscosity. M1, Redline, AmsOil all failed. A long time ago (10 odd years) there were a couple of xxW-30 oils that had HTHS viscosity above 4.0 cP.
