For occasional track use , which oil viscosity to use? Using oil data sheet for guidance

[Jester04]

Any issues if you were to use 5W-30 year round?

Not really! Remember if you have a oil the first number either 0W or 5W or whatever you choose is how well it flows in colder temps. If you live in a colder climate then lower numbers will help you since the oil will flow better and more quickly at those cold temps. Heavier oils will be thicker and not flow as well so you might not have the best lubrication on initial startup up if its freezing.

Where I’m at its so hot that 5w or 10W will flow very well since its always hot here in FL. When the cold temp of the oil will be in the 80F degrees just sitting. So just use the right one for where you live. If it snows and its freezing and you actually drive the car in winter then 0W is great.

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[Cornercarver]

0W-20? 5W-20? 0W-30? 5W-30? 10W-30?

I've done 2 HPDEs and oil temps have reached temporarily 275F which is quite high but not sustained. I live in a very hot tropical climate with 90+F ambient temperature on track days. I've been researching into which oil viscosity to use but there's so much conflicting information out there that I don't know which way is up. I'm currently using AMSOIL signature series oil 0W-20.

For example, some of the technical data is counterintuitive on this AMSOIL data sheet, such as:

• Some lower weight oils having higher viscosity indexes than heavier weights (0W-20 higher than 5W-20), although my understanding is that 5W-20 is actually somewhat better in high temps than 0W-20 (although same high temperature 20 rating).
• Same issue with NOACK volatility % weight loss (5W-20 having less volatility than 0W-30)

I would assume Hight-Temperature/High-Shear Viscosity is one of the most important data points but then again, I'm not entirely sure, this data point follows what one would expect in terms of having higher value in direct proportion to higher weight.

According to these data in the table, which would you chose? Which property is more significant or important for our K20C1 for occasional heavy track use and high temps?

Thanks in advance

[/QUOTE
I'll see your 'very hot tropical climate with 90 degree ambient track temps' and raise you one unbelievably hot desert climate with 130-140+ degree track temps.
So don't feel too bad. It could be worse.
That said, other than heat soak, no oil issues using OEM oil type, no breakdowns. But there is a definite difference in performance on cooler days, because turbo, right?

 

[keller]

I live in similar weather and I run motul 300v 5w30. My UOA results are fine. Few people run 40w oils on this engine, unless built. A good 20w oil should be fine, as long as you have good oil pressure.

Note that changing the oil weight will make your oil temp "readings" inaccurate.

 

[Jester04]

I live in similar weather and I run motul 300v 5w30. My UOA results are fine. Few people run 40w oils on this engine, unless built. A good 20w oil should be fine, as long as you have good oil pressure.

Note that changing the oil weight will make your oil temp "readings" inaccurate.

How will it make them inaccurate?

 

[keller]

How will it make them inaccurate?

The oil temp is calculated, there's no oil temp sensor in our k20c1s. The ECU uses ECT and OilP as input, both of which depend on the oil weight.

 

[007]

We need a dedicated thread like this with a poll.

 

[Jester04]

The oil temp is calculated, there's no oil temp sensor in our k20c1s. The ECU uses ECT and OilP as input, both of which depend on the oil weight.

Cool! Did not know the ECU was assuming oil temps through oil pressure and and engine coolant. Good to know! Thanks

 

[Fresh]

The oil temp is calculated, there's no oil temp sensor in our k20c1s. The ECU uses ECT and OilP as input, both of which depend on the oil weight.

Any idea on the correction factor for non-OEM weights?

 

[keller]

Any idea on the correction factor for non-OEM weights?

Not really. I noticed my peak oil temps on track went "down" from 123C to 118C when I moved from 0w20 to 5w30. I believe it should be the opposite, but I assume the higher OilP is affecting the calculation. I just consider my calculated OilT to be 10-15C wrong at all times. This is on an FK8 btw.

I have seen a report of LogR being 16C wrong on a track and 1-2C during street driving. And he was using 0w20.

 

[CTRifecta]

Just did an oil change and swapped my 0w20 out for 0w40, and initial impressions are that oil pressure is up approx 5psi across the board. I expected a slightly higher pressure, but posting here in case others are curious.

Oil temps seem to be calculating the same as with the 0w20. I was expecting lower calculated temps but not seeing that on the logR. Will see if I notice anything as the days go on.

For those interested, I used to see steady state pressure of 73psi at 69mph cruising, now I see 77-78psi. Idle psi was 19-20, now 24-25psi.

Before the oil Nazis crucify me, just sharing my data, not looking for your opinion..

 

[tezzasaurusrex]

I've run Honda 0W20 Ultra Leo and Motul 8100 Eco Clean 0W30 on track, and found no discerable wear differences from either oils based on the UOA test reports I got back.
I did notice however that the Honda Ultra Leo oil has a better anti-wear additive package than the Motul.

 

[Fresh]

So I've mostly seen Motul and Amsoil as the two most recommended split DD/racing oils on here.

With that said, I'll likely do 5w-30 (but maybe 10w-30 since I don't really plan to start/drive in cold weather likely ever since this isn't my DD, but not sure which of the following... any recommendations?

SIGNATURE SERIES 5W-30 SYNTHETIC MOTOR OIL
DOMINATOR® 10W-30 RACING OIL

There is also a chance I'm entirely wrong, but I want to go with what the trackers out there know...

EDIT: After reading more, I think I'm leaning towards the 0W-30... I wasn't aware the first number was rated at 104F... this means if you're truly a colder start, your 5W and 10W aren't ever going to flow like the 0W... which I think is pretty important...

SIGNATURE SERIES 0W-30 SYNTHETIC MOTOR OIL

 

[Icehawk]

Looking at lots of charts online and unless you are seeing temps below freezing a 5W or 10W is what I'd be using personally. I'm in SoFla so I'm absolutely not going to run a 0W when I get the oil changed soon especially as I'm hoping to get a few track days in once it cools off here.

 

[Jester04]

So I've mostly seen Motul and Amsoil as the two most recommended split DD/racing oils on here.

With that said, I'll likely do 5w-30 (but maybe 10w-30 since I don't really plan to start/drive in cold weather likely ever since this isn't my DD, but not sure which of the following... any recommendations?

SIGNATURE SERIES 5W-30 SYNTHETIC MOTOR OIL
DOMINATOR® 10W-30 RACING OIL

There is also a chance I'm entirely wrong, but I want to go with what the trackers out there know...

EDIT: After reading more, I think I'm leaning towards the 0W-30... I wasn't aware the first number was rated at 104F... this means if you're truly a colder start, your 5W and 10W aren't ever going to flow like the 0W... which I think is pretty important...

SIGNATURE SERIES 0W-30 SYNTHETIC MOTOR OIL

It really depends on where you live, the first number is rated for winter. And like you said the lower the number the better if flows. Me living in Florida the oil sits at 70+ degrees in the garage so it will still flow well. I like my oils to have the least amount of spread since it helps with shearing. I will use 5w-30 for winter and 10W-30 for summers.

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