Any reason to NOT switch to 5w30?

[FLtrackdays]

It's not that simple. That's a bit like asking "If the EPA requires that cars meet X mpg, then why don't manufacturers just build all cars to meet X mpg while keeping everything else about the cars the same as they always were?"

There are competing requirements at play. Long-term reliability, gas mileage, and output power form a triangle. Engineering advancements have allowed manufacturers to increase the size of that triangle slowly over time, but you can't just come along one day and crank up one of the legs (mileage) without negatively impacting the other two. There's only so much the manufacturers can do, and long-term reliability (past the manufacturer warranty period) is pretty much the first to get cut when they run into that wall.

You have to remember, the user manual and its oil recommendation is not written by the engineers, it's written by the marketing and legal teams. I've been on the other side of that conversation and written user manuals that later got hacked and slashed by marketing until it barely even resembles what was originally written. They take phrases like "we recommend using X, but the absolute limit of the design is Y" and turn it into "we recommend Y and nothing else" simply because it lets them advertise better numbers without legal pushback.

What I want to know is, why are some people so comfortable with swapping out everything else about the car (coolant, radiators, brake fluid and pads, rotors, etc.) for applications that need it, but are so insistent that oil be unchanged? What makes those people so sure that a stock power grocery getter in Alaska needs to run the exact same oil as a tuned track car in Florida? Hint: they don't.

Right on

For me, I‘m not worried a bit about using a higher viscosity that other race guys (pro or amateur) use in their B58 track cars - here in hot as balls Florida. I don’t think 0-20 will hurt either. It simply doesn’t fit my need best. Bryan (Razorlab) has a great build page if anyone is thinking about tracking more often. If doing lots of highway driving, what’s the point of going with a higher viscosity? Do what you feel is best @EvilMKV for your use.

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[EvilMKV]

So well said!

For me, I‘m not worried a bit about using a higher viscosity that the race guys use in their B58 track cars - here in hot as balls Florida. I don’t think 0-20 will hurt either. It simply doesn’t fit my need best.

What do you run in yours? I'm also in FL and hot as balls is right lol

 

[FLtrackdays]

What do you run in yours? I'm also in FL and hot as balls is right lol

At summer temps, at least out here, the difference of the W # is like 1-2 in viscosity as the oil is already 100°f during "cold start". Literally makes no difference if you use a 0w30 or 5w30 in summer out here.

The biggest difference in the oil is that the 0w30 has more additives to make the split bigger so technically it will break down sooner.

Love Evo’s rational. But without his mechanical background, I just ask the mechanics or pro drivers at our local Homestead and Sebring tracks. I switched to Liqui Molly 5-30. However, I don’t think you need to rush out and change your 0-20 unless you’re having an issue.

Found a very nice thread/post on it:
https://www.supramkv.com/threads/toyota-gr-supra-owner-manual-navigation.1845/

Anyways from a Europe manual (MY21, B58TU1 or updated motor):

And thanks to @Tsuki8, you can see 0-40, 5-40 would work too. For those that need to see it in writing.

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