I am in CA and use 15-50. The Racer's Group Cup cars here in the Bay run that oil grade. I never tried 0 or 5-50. Anyone currently running this grade?

 

The first number corresponds to how quickly the oil flows at
32 degrees farenheit. A '0' indicates it flows within a range
close to simple 0-weight single-viscosity oil. The second number
is how it flows at 100 degrees centigrade. Because of
viscosity enhancers, a 0-40 oil flows more like a simple single-
weight 40-weight oil would at that temperature. Thus multi-
viscosity oils (those with viscosity enhancers) stay closer to
the same thickness over a wider range of temperature. This
is particularly valuable mechanically in keeping a constant
film thickness, and also in flowing quickly to parts that may
be dry from sitting with the engine off.
Joe

 

You may be onto something too. Oil manufacurers have
recently been making compromises between lubricity,
protection and emmisions. They have dropped back on some
additives because they contribute to smog-measured
emissions, so oils that are labelled for trucks may allow them
to be better, at the cost of more emissions, but not in the
car fleet that is getting the emissions attention...
Joe

 

Anyone like the racer's group that is aiming for road racing
may well want an oil that does it's best hot. A stop-and-go,
frequent-cold-start car may still do better with what the
manufacturer says... Heck, racers often run single-weight
oils. Racing is extreme, but it is simpler too. It's always hot
and hard.
Joe

 

I was at the TRG open house back in April and talked to one of the mechanics about this. He told me that they were using 0W-40. He cited slightly better HP as the reason.

I am not sure that race experience is the best guide for determining oil choice. Remember that these motors get rebuilt at least once a year.

 

You have to put oil in these things????

 

OHH ****!!!!

 

Thanks Joe!

 

The first viscosity number refers to a viscosity spec. at very low temps, -25 to -35C. A 5w30 oil if frequently thinner at 32F. than 0w40.
Oil blenders can also get a wide viscosity range by adding pour point depressants to a thicker base oil (vs. adding viscosity index improvers to a thin base oil).

 

This is all good info. So with the new grades, and availability aside, what would be the best choices for
1. Street application, in cold/medium weather
2. Street application, in medium/hot weather
3. Race application, in cold/medium weather
4. Race application, in medium/hot weather

 

For street, do what Porsche recommends, 0-40 up to
about 70 degrees ambient, and I'd stay there for
higher temps too if I did a lot of stop and go, and
not a lot of long hard driving. I'd want a 15-50 or
ideally a 0-50) for long hard hot driving.

For racing, typically the ambient temperature isn't as much
an issue. The motor is going to be at full-hot, so you
might want a straight 40 or 50 weight. The viscosity
modifiers break down over time, so you want the
stability of single-weight oils when you have a largely
constant temperature environment. However for cars
like ours that depend on quick thin oil for the valve train
hydraulics, maybe I'd do what TRG says (0-40).
Joe

 

Thanks much Joe! Very helpful.

 

Anyone figure out where to get the Mobil1 5W-50 yet. After more reading I'm not sure I want to run 0 anything the way I use the car. Thanks

 

I just put the 5w50 suv Mobil in last week. Available here at Walmart. You can also use the Castrol Syntec 5w50.

 

The M1 SUV oil is 5w40. For some reason Castrol 5w50 was removed from Porsche's approved oil list.