What oil will you use?
 

What oil do you plan on using?

I dont trust 20W oil in general, it has been responsible for many premature engine failures in modern cars trying to get the best eco figures possible. Unless it voids the warranty, I will use 5W30 (dino in break in period, synth after break in)

Thought it came with synth from the factory?

I would be hard pressed to accept that any 0W-20 was anything other than synthetic, depending on what you think synthetic actually means. In order to meet volatility requirements a 0W-20 is unlikely to use much conventional Group I base oil.

It is specified as required because 0W-20 is what they would have used for EPA emissions and fuel economy testing.

While you can't void a warranty, the dealership will certainly attempt to -- and likely succeed in -- void any warranty claims regarding the powertrain when they find out you were using oil not specified in the manual; even if that oil likely provides better protection.

That is where is can become dicey. The manufacturer has a vested interest, relating to CAFE requirements, in ensuring that the oil used for EPA certification is used in practice.

OW-20 should be able to work acceptably if an engine is appropriately designed.

You do have an out however:

"....Oil viscosity (0W-20 is explained here as an example):
• The 0W in 0W-20 indicates the characteristic of the oil which allows
cold startability. Oils with a lower value before the W allow for easier
starting of the engine in cold weather.
• The 20 in 0W-20 indicates the viscosity characteristic of the oil when
the oil is at high temperature. An oil with a higher viscosity (one with a
higher value) may be better suited if the vehicle is operated at high
speeds, or under extreme load conditions....."

which shows in both the BRZ & FRS owners manuals!

Now this is good news. Mine will be seeing "extreme load conditions" so I guess that can provide a justification for my choices xD

I may switch to 5W-30 for DD/AutoX use, then switch back to 0W-20 for long trips.

Recall, short trips (less than something like 3-5 miles) also fall under extreme load conditions and hard wear because the oil never actually gets to temp.

I plan to use Amsoil. Probably 0W-20 Signature at first, but switch to 0W-30 for HPDE events.

Well sort of, but not load in the sense that you might be thinking. Short trip driving stresses oil because yes it does not get up to temperature enough to evaporate any condensation from the crankcase. But oils are specifically designed to deal with the condensation issue. This performance area has nothing to do with viscosity grade.

Fuel dilution can also be an issue for cold start short trips, but much less so with accurate fuel injection. However if you are over reving when the engine is cold there is still some potential for over fueling which can get into the crankcase and dilute the engine oil. Still wise to take it easy when and engine is warming up.

They want 0W for best low temperature starting and oil delivery when cold. The lower the second part eg. 20, 30, 40..., which relates to high temperature viscosity performance the better the fuel economy.

Sooooo....which oil are you guys gonna use? Mobil 1, AMSoil, Walmart value, or vinegar oil?

Im leaning towards Mobil 1 or AMS oil. Have never used AMS oil but I am curious about it. I know for sure I will be using that stuff moto uses in his. Forgot what its called :p

As described, the number before the W indicates the cold viscosity and the number after the W indicates the hot viscosity properties of the oil. Given that this car calls for an oil that has low viscosity at low temperatures, 0W, I would stick with something that also is a 0W. But the Higher number is a little ambiguous. The lower the number is, the more the oils viscosity drops as it gets how. Changing to an oil with a higher number after the W will give you a more temperature stable oil more then anything else. The viscosity at normal operating temperature wont be effected much, but will remain in the correct operating range for the engine for a higher temperature.

I'll be running Mobile 1 0W40.