VR1 Oil Weight for Built Turbo
 

After hearing VR1 preached as god's miracle juice from quite a few local shop owners and gear heads I trust, I'm giving it a shot.

Im not a professional, but I've read over the general information about oil weights for different applications and have been leaning 10w-30 versus the 20w-50. After seeing a spread of opinions though, I'm still curious about what thoughts/suggestions the more informed individuals here have.

Here's the setup/usage:
- I previously ran T6 5w-40
- Boundary stage 1 pump (~15-60psi warm)
- Supertech/Wiseco/ACL Race for Pistons/Rings/Bearings
- Clearances in the attached picture
- Currently installing a setrab 25-row cooler, 180* thermostat (likely behind the rad after removing the 2nd fan)
- 255hp @ 11psi (autox/track tune). 350hp @ 19psi (street tune). Planning to eventually try 23-24psi after a drivetrain upgrade.
- Car will be 60% street driven on weekends, 40% HPDE/track/autox driven.
- I live in DFW so the temp swings can be large. Definitely 10w-30 in winter.

My current line of thinking is that the Setrab will consistently keep temps ~180 and 10W-30 will be the correct weight, but please enlighten me.

https://cimg3.ibsrv.net/gimg/www.mia...c36f89b6ad.png

You already know the viscosity should be chosen based on usage and 20w-50 has no business being in a primarily street driven application.

If you want to be super duper safe then log oil temps with the new cooler and make sure they're not excessive on track. If they are then improve oil cooling or swap oil for track days. I don't believe it's realistic to expect oil temps around 180F but I'd allow much higher before I considered 20w-50.

Today I learned that there's a synthetic VR1. I may try this in the miata now if I can find info on how it does at high temps. I ran Rotella T6 5-40 but switched to Mobil 1 due to my high oil temps, and gained oil pressure at hot idle. If you keep your oil temps where they should be then the 10-30 would be what I'd use instead of 20-50.

Been running the normal VR1 in my Jeep cause flat tappets; it's great.

Definitely not 10-30 for your power goals and main clearances. I would go with a 5,10,-40wt unless you are going to the track and then would step up to a 50wt.

Thanks, great feedback. Im learning a few things here that seem obvious now, but it's been years since I've had my Miata at events and it was just N/A with aftermarket suspension. Didn't put 2 thoughts into oil then...

I'll go back and re-read the oil cooler reviews. I thought I remembered reading that a properly set up setrab 25-row w/ 180* thermostat would keep temps ~180-200 at events, but the more I think about it, the less possible that sounds this is not possible.

Sounds like ~210-240* should be expected at events so maybe the 20-50 then, but it's back to the T6 5/10-40 unless there's a new champ in that weight range.

Refs:
https://www.miataturbo.net/race-prep...3/#post1153739
https://www.miataturbo.net/engine-pe...-i-use-100575/

Have you considered using a higher ester oil like Motul or Redline? I prefer the 5-40 Redline for the street and the 10-40 racing for the track. 200-220F is the sweet spot, but in autox you may run a bit lower and 1/2hr HPDI events you may run up to 250F. Mid 200's is not an issue for good oil.

There can be a correlation between thicker oil and higher oil temperatures at sustained high RPMs, FWIW. My oil was cooler at the track with 40 weight than 50 weight and didn't have lower pressure. Can't tell you what the difference in temp was. Can't tell you if there's a difference in film strength between 50 at a higher temp and 40 at a lower temp either. I can think of an argument for both and don't have the necessary data to support or refure a hypothesis.

Came for a binary pick, left reading scientific journals about hydrolytic stability and the chemical competition between esters and high-pressure oil additives like zinc due to molecule polarity. Typical.

Keynotes: Redline/Motul = good

The zinc is a carrier for the phosphorous which is the actual EP additive.

I believe it could be possible that the higher viscosity would run hotter, but not sure if it would be enough to actually reduce the dynamic viscosity by 15-20%. Maybe there is more of a benefit at higher temps. As I have mentioned before the aftermarket pumps have more restrictive passages which might also increase the temp because of the increased friction. It appears that 40wt seems to be very common among HP OE designs, motorcycles etc. I have noticed in some models that offer several performance levels such as the current Mustangs that they start at 5-30 and move up to 5-50 for highest output version.