Rotella T4 15w40 + Lucas in a 93 Corvette Autocross Race Car

[Robvette]

You are obsessed with the cSt viscosity.

I’m pretty sure that was the first time I mentioned cSt in this 5 page discussion.

Referencing T4 + Lucas as “just over 18” simply shows that the combo results in a verified 50 weight oil.

Fwiw - here’s the HTHS of the 2 oils I’m using:

M1 15w50 has a HTHS of 4.5. And the HTHS of Supercar 5w50 isn’t published but it’s suspected to be similar.

 

[SubieRubyRoo]

Cheap + engine didn't explode = god's gift to engines

People will go to great lengths to justify saving a buck. If Rotella was to suddenly go to $50/gal, they'd drop it in a hearbeat.

That crowd is probably big on using MotorKote as well

 

[cheesepuffs2]

It doesn’t seem to consume 50 weight oil. I’ve only owned this car for 6 days tho.

The Prius example wasn’t necessary. It just illustrates that 30 was the still the baseline 17 years ago and bumping up a viscosity grade has no negative effects and it reduces oil consumption. It also reduces engine wear.

Again, thicker oil "reduces engine wear" cannot be used as a blanket statement. The reason why some recommend running a thicker oil in older engines is to reduce burning like we talked about, plus it can reduce weeping from old gaskets, and finally because there's an idea that as bearing clearances open up with wear over many years of use that a thicker oil will bump oil pressure back up a bit if any oil pressure had been lost. But if oil temps are reasonable then you won't gain any appreciable protection from wear by going to a 50 weight.

A couple examples of engines that actually call for 50 weight from the factory would be the (modern) Mustang GT350, which spins to much higher RPM and is way more power-dense than an old LT1, and Harley-Davidson engines (across the board) which are air-cooled or air and oil cooled (depending on which engine family) and have one cylinder blocked from direct air flow while in motion. Those are cases where 50 weight will reduce wear compared to thinner oils because those conditions are going to be pushing thinner oils to the brink. But if an engine isn't as demanding on it's oil then the extra viscosity is headroom that won't be utilized, and frankly a stock old LT1 with a functional cooling system isn't going to be taxing on oil. Great engine, don't get me wrong, but it isn't a race engine.

 

[ZeeOSix]

But if an engine isn't as demanding on it's oil then the extra viscosity is headroom that won't be utilized, and frankly a stock old LT1 with a functional cooling system isn't going to be taxing on oil. Great engine, don't get me wrong, but it isn't a race engine.

If that car was tracked on top of Auto-X use, I'd run a stout xW-40 for both events for simplification since oil temps will be much higher on the track than in a 60 second Auto-X run, especially when the oil probably isn't even at full operating temperature when the Auto-X run starts. Running a xW-50 on the track isn't going to hurt however, but a good xW-40 should still give adequate protection on the track IMO.

 

[CleverUserName]

An example that could never exist, but yes the point is that the HTHS (and even beyond that, the HTFS) is what ultimately matters.

Of course it could exist. If a 0w20 had a density > 1.0, it would have a high HTHS.

 

[ZeeOSix]

Of course it could exist. If a 0w20 had a density > 1.0, it would have a high HTHS.

If you understand how oil if formulated in order to make a mulit-grade oil, you will never be able to make a 0w20 and a 15w50 have the same HTHS like you posted earlier.

 

[gfh77665]

Here we go with the Lucas again.

Here we go with HPL again.

 

[userfriendly]

That crowd is probably big on using MotorKote as well

Naw, when I run out of Rotella I reach for a pail of Delo TorqForce MP or 50.
The new 6.6L truck engine would be an interesting animal in this car.

 

[CleverUserName]

If you understand how oil if formulated in order to make a mulit-grade oil, you will never be able to make a 0w20 and 15w50 have the same HTHS like you posted earlier.

I beg to differ. If there were base oil(s) that existed which had a high density it could both meet 0w and HTHS specs. It doesn’t currently exist but saying it’s not possible isn’t true. It is 100% possible

 

[SubieRubyRoo]

Naw, when I run out of Rotella I reach for a pail of Delo TorqForce MP or 50.
The new 6.6L truck engine would be an interesting animal in this car.

I meant the crowd that uses Rotella for “off-label” uses, not things it’s actually designed to be used in.

 

[ZeeOSix]

I beg to differ. If there were base oil(s) that existed which had a high density it could both meet 0w and HTHS specs. It doesn’t currently exist but saying it’s not possible isn’t true. It is 100% possible

You do realize that HTHS viscosity is the viscosity at 150C (302F) and a shear rate of 1 million/sec. You think a multi-grade oil in 0W-20 could be formulated to have the same HTHS as a 15W-50 as you claimed? Don't think so. Maybe David at @High Performance Lubricants can chime in and tell us ... my bet is no way.

 

[CleverUserName]

You do realize that HTHS viscosity is the viscosity at 150C (302F) and a shear rate of 1 million/sec. You think a multi-grade oil in 0W-20 could be formulated to have the same HTHS as a 15W-50 as you claimed? Don't think so. Maybe David at @High Performance Lubricants can chime in and tell us ... my bet is no way.

The 15w50 is an example. There are 10w30 which currently exist that have a HTHS of a 5w40. 15w40 that have and HTHS of a 20w50. These are high VI high density lubricants.

How do you know what is possible if it doesn’t exist yet? Could an engineer from 1950 predict what they can formulate now?

 

[ZeeOSix]

The 15w50 is an example. There are 10w30 which currently exist that have a HTHS of a 5w40. 15w40 that have and HTHS of a 20w50. These are high VI high density lubricants.

The only oils I've seen where one grade lower barely breaks into the minimum HTHS spec (per J300) of the next grade up are oils with no VIIs, so they retain a higher HTHS viscosity due to less shearing at the 1M/sec shear rate. But your claim of a xW-20 having the same HTHS as a xW-50 isn't going to happen, even if the xW-20 is a no-VII formulation. It might barely break into the minimum HTHS for a xW-30 with VIIs ... but not meet the minimum HTHS for a xW-40 or 50.

How do you know what is possible if it doesn’t exist yet? Could an engineer from 1950 predict what they can formulate now?

I'm waiting for the anti-gravity machine to be invented so that electricity can be generated by a gravity delta field. That will probably happen before xW-20 oil has the same HTHS as a xW-50, lol.

 

[RDY4WAR]

Folks are assuming that 30 is the baseline optimal oil weight and provides the best protection in all conditions for SBCs (small block chevy’s).

I personally believe that, when new, 40 is the best SBC daily driver viscosity. And, that 50 has additional benefits in SBCs - especially when temps are hot and / or track days. If you live someplace very cold 5w50 would be preferable to 15w50.

Also, I definitely subscribe to the approach of moving up one viscosity level when an engine becomes high mileage - especially if old and high mileage.

View attachment 173905

Having built, raced, tore down, rebuilt, and sampled many SBC engines, that just simply isn't case. The viscosity is dependent on 3 factors...

1. Operating oil temp
2. Rod and main bearing clearance
3. Load on those bearings

None of those really change with age in a healthy engine, including the clearance. If you wear the bearings so much that you have to increase viscosity to fill the void, you have much bigger issues than what oil to use. I've torn down a number of junkyard SBC and BBC engines, with more than 200k miles, where the bearing clearances are still within OEM tolerance for new assembly.

If anything, a higher viscosity oil than necessary can contribute to bearing fatigue due to a combination of reduced flow and increased hydrodynamic friction making the bearing run hotter. On top of that, higher viscosity has a higher specific heat capacity meaning it will peak at a higher temperature and be more difficult to cool off. It's also more naturally susceptible to aeration problems, which can lead to bearing cavitation in extreme cases.

If you use a quality oil for the task from the get-go, in the appropriate grade, and you'll be highly unlikely to have any bearing issues.

 

[RDY4WAR]

That crowd is probably big on using MotorKote as well

Right. Forget using a proper oil for the application. Pay more for a junk oil and a supplement of iron cancer, that's the Brotella way.

 

[userfriendly]

I meant the crowd that uses Rotella for “off-label” uses, not things it’s actually designed to be used in.

The only thing that I can’t understand is why the same three or four bitog members care what others do.
Now we have daily “Brotella” bashing posts, and for what? Likes and validations?

 

[SubieRubyRoo]

The only thing that I can’t understand is why the same three or four bitog members care what others do.
Now we have daily “Brotella” bashing posts, and for what? Likes and validations?

Not sure. I’ve definitely used my share of Rotella T6 in the past. I moved to Delo XLE and Delvac ESP 5w40 mainly because I got them on clearance, about 25 gallons for about $80.

I know there’s plenty of people here that use the lower T# Rotellas in OPE and motorcycles. It’s still a fine oil for its intended purposes.

 

[SugarMouth]

Any reason why a 5W-40 Euro oil would not do well in an autox vehicle?

 

[OVERKILL]

The 15w50 is an example. There are 10w30 which currently exist that have a HTHS of a 5w40. 15w40 that have and HTHS of a 20w50. These are high VI high density lubricants.

How do you know what is possible if it doesn’t exist yet? Could an engineer from 1950 predict what they can formulate now?

You will run into the KV limits for the grade first. Remember, the ceiling for an xW-20 is 9.3cSt, for a 50, it's 21.9cSt.

If you take a base oil that's an xW-20, so we'll use SpectraSyn 8cSt PAO, it has an HTHS of 2.58cP. There's no VII to shear there, that's the HTHS of a pure PAO base oil, which, unsurprisingly, happens to be the same as the HTHS lower limit for the xW-20 designation.

The PDS for some of the heavier PAO bases like SpectraSyn 10 doesn't have the HTHS listed, but, if we look at the xW-20 with the highest HTHS in @High Performance Lubricants no VII series engines oils, this is the Euro 5W-20, with an HTHS of 3.267cP and a KV100 of 8.7cSt. This is a significantly higher HTHS than all the other mono xW-20's, including those with a higher KV100, including the Euro 10W-20, which is 9.09cSt (so right at the upper edge of the xW-20 grade), with an HTHS of 2.795cP.

So, if Dave were to take the same blending approach (which I assume is using mPAO to get that HTHS) but try to get the KV100 right at the upper limit of the xW-20 grade, so 9.29cSt, I suspect you might be able to get to an HTHS of ~3.4cP, which is just below the lower limit for 0W-40/5W-40/10W-40. The lower limit for an XW-50 is 3.7cP and they are typically significantly higher than that. HPL 5W-50 has an HTHS of 5.005cP for example.

So, there ARE limitations here.

 

[SugarMouth]

Having built, raced, tore down, rebuilt, and sampled many SBC engines, that just simply isn't case. The viscosity is dependent on 3 factors...

1. Operating oil temp
2. Rod and main bearing clearance
3. Load on those bearings

None of those really change with age in a healthy engine, including the clearance. If you wear the bearings so much that you have to increase viscosity to fill the void, you have much bigger issues than what oil to use. I've torn down a number of junkyard SBC and BBC engines, with more than 200k miles, where the bearing clearances are still within OEM tolerance for new assembly.

If anything, a higher viscosity oil than necessary can contribute to bearing fatigue due to a combination of reduced flow and increased hydrodynamic friction making the bearing run hotter. On top of that, higher viscosity has a higher specific heat capacity meaning it will peak at a higher temperature and be more difficult to cool off. It's also more naturally susceptible to aeration problems, which can lead to bearing cavitation in extreme cases.

If you use a quality oil for the task from the get-go, in the appropriate grade, and you'll be highly unlikely to have any bearing issues.

How about lifters? Same opinion as for the bearings?

What is your go to oil weight for a SBC which would see some additional heat and load over a daily driven vehicle?