Non-dexos oil

KARNUT · April 25

From time to time I watch the oil geek. I stumbled on oil viscosity comparison between 0-20 and 5-30. What is better. In his test 0-20 offers better results unless you have a gas dilation. Of course some oil is better than others. That’s another test. It’s reasonable to assume that light weight to start would move faster. And heavy weight would protect better after warming up. That’s not the case on the heavy end according to him. It all comes down to intrusion. Yet some manufacturers say extend. The fine print says unless extreme conditions exist. The finer print says unless you’re hauling your ride on a flat bed, everything is extreme. Before I went to more frequent oil changes we just bought my wife’s new Genesis. Normal oil changes are 7500 mile oil changes. I took it in at 5K for the first one. We worked into the deal bumper to bumper 10 years 100K warranty. I not trusting a startup model made it a condition for purchase. They informed me that Texas heat falls under extreme and oil change should be 3400 miles. I looked at him and asked how does the engine know? It has a thermostat it reaches operating temperature and that’s it. I figured that warm climate would benefit at start up. His eyes glazed over and I said fine. I didn’t want to jeopardize the warranty. All these years later the oil never gets dirty on the stick. After the warranty I went up to 5K oil changes. Oil stays clean looking in my vehicles. Even the Odyssey cleaned up after going 127K miles on the minder about 8-10k oil changes. Yea the kids don’t listen. She does the same with the CRV I swapped her with. Same with my grand daughter who now drives my Camry. Good field test though seeing how long they go.

Grumpy Bear · April 25

4 hours ago, KARNUT said:

They informed me that Texas heat falls under extreme and oil change should be 3400 miles. I looked at him and asked how does the engine know? It has a thermostat it reaches operating temperature and that’s it.

Oil temperature is not as closely related to water temperature as you might think. Oil temp is indeed related to air temperature AND to load and rpm. Ya like measurement and science...here it is.

Pepper in the winter runs about 175 F oil and has a 180 F water thermostat. In July she runs roughly 200-210 F on oil. Both temperatures are running 55 mph. Run 55 mph in fourth gear and it will run up past 250 F. Not uncommon pulling a trailer loaded at max GVW and this wasn't. Drop 7 K lbs on that trailer and you can cook road kill.

I don't recall how many times I've posted this chart but a bunch. This is high gear with changes only in road speed for three different water thermostats and three different base oil packages for the center water thermostat. All within 5 degrees air temperature over the exact same roads in winds under 10 mph.

Bottom line is water temperature does not regulate oil temperature to within a few degrees of water temperature.

That nearly 18 degree F oil temp swing from cold to hot cuts oil life in half. The Arrhenius rate rule states that for every 10°C (18°F) increase in oil temperature above 60°C (140°F), the oxidation rate roughly doubles

The bold in the quote above is the oxidation onset temperature of mineral oil. Synthetics, by type, are higher to start the process but the 'rate' is the rate. Double per 18 F (10C).

asilverblazer · April 27

On 4/25/2026 at 12:31 PM, Grumpy Bear said:

Oil temperature is not as closely related to water temperature as you might think. Oil temp is indeed related to air temperature AND to load and rpm...

Bottom line is water temperature does not regulate oil temperature to within a few degrees of water temperature.

I'm curious why water temperature DOESN'T control oil temperature, alternatively, what IS the driving factor of oil temperature?

Ambient I understand from a starting temperature, but I would expect that to have less effect over operating (run) time. (Ignoring any eternal oil coolers)

RPM makes sense, as "work" being put into the oil, friction the oil is experiencing and the result is heat.

I have mixed opinions for 'load': The only effect load should have is that it takes more fuel and air to move the piston the same amount. I guess given that, then the increased air and fuel makes a bigger combustion, resulting in more heat. Though I don't see that directly effecting the oil temperature any more than it effects water temperature (by appearances, it effects water temperature so indirectly - literally by the warming the metal around the water jackets - that I've never seen water temperature spikes on the gauge, regardless of load, rpm ambient or any combination of).

Other thoughts, the volume of water in the cooling system is different/larger. The cooling system and oiling system serve fundamentally different purposes...

BUT! What if the oiling system served the purpose of the cooling system? With a few adjustments, larger capacity/flow to control the effect of 'spikes in load/rpm'. Presumably then being able to eliminate an entire sub system in the vehicle (cooling) and accomplishing it with a more robust oil cooling system.

Grumpy Bear · April 27

14 minutes ago, asilverblazer said:

I'm curious why water temperature DOESN'T control oil temperature, alternatively, what IS the driving factor of oil temperature?

Ambient I understand from a starting temperature, but I would expect that to have less effect over operating (run) time. (Ignoring any eternal oil coolers)

RPM makes sense, as "work" being put into the oil, friction the oil is experiencing and the result is heat.

I have mixed opinions for 'load': The only effect load should have is that it takes more fuel and air to move the piston the same amount. I guess given that, then the increased air and fuel makes a bigger combustion, resulting in more heat. Though I don't see that directly effecting the oil temperature any more than it effects water temperature (by appearances, it effects water temperature so indirectly - literally by the warming the metal around the water jackets - that I've never seen water temperature spikes on the gauge, regardless of load, rpm ambient or any combination of).

Other thoughts, the volume of water in the cooling system is different/larger. The cooling system and oiling system serve fundamentally different purposes...

BUT! What if the oiling system served the purpose of the cooling system? With a few adjustments, larger capacity/flow to control the effect of 'spikes in load/rpm'. Presumably then being able to eliminate an entire sub system in the vehicle (cooling) and accomplishing it with a more robust oil cooling system.

Thoughtful question.

You nailed it on RPM.

Load. a 4" piston has a nominal crown surface area of a bit over 12.5 square inches or 100 square inches total for a V-8 motor. 480F to 840 F is a typical crown temperature. And what is on the other side of the crown? Oil. In many motor oil jets are used to run these temperatures near the max. An efficiency move. That oil that cools gets heated.

https://zenodo.org/records/19482246/files/Piston Head Strength and Heat Dissipation in Internal.pdf?download=1

PunchT37 · April 30

Rpm and something called bearing speed. This tears up oil.

Not crank speed but bearing speed. As the journal size increases, bearing speed does. In other words, imagine a 2.5 main turning 5000 rpm. Then, a 3 inch journal turning 5000 rpm’s. The bearing length increases for the same rpm. Lots more heat generated.

I have an engine with a 3.25 main. I can turn this thing to 6400 rpm. I run 10w30 most of the time. If I race it, it gets 20w50. If I run 10w30, especially in the summer, while racing, you will roast the bearings as the oil thins too much and allows the crank and bearings to touch.

All this gets worse as rpm’s go up. No matter the journal size. BUT, the larger the journal, the more intense conditions the oil has to face.

So, rpm’s, bearing speed, and heat. This includes towing on hot days.

Now one can see a 6.2 liter engine running on 87 octane, towing, in the summer, with 0w20 oil. Add long oci to the mix.

Not discounting the crank roughness. You will sheer the piss out of the oil. Spun bearings are in your future.

No F-bdy Bs · April 30

1 hour ago, PunchT37 said:

Rpm and something called bearing speed. This tears up oil.

Not crank speed but bearing speed. As the journal size increases, bearing speed does. In other words, imagine a 2.5 main turning 5000 rpm. Then, a 3 inch journal turning 5000 rpm’s. The bearing length increases for the same rpm. Lots more heat generated.

I have an engine with a 3.25 main. I can turn this thing to 6400 rpm. I run 10w30 most of the time. If I race it, it gets 20w50. If I run 10w30, especially in the summer, while racing, you will roast the bearings as the oil thins too much and allows the crank and bearings to touch.

All this gets worse as rpm’s go up. No matter the journal size. BUT, the larger the journal, the more intense conditions the oil has to face.

So, rpm’s, bearing speed, and heat. This includes towing on hot days.

Now one can see a 6.2 liter engine running on 87 octane, towing, in the summer, with 0w20 oil. Add long oci to the mix.

Not discounting the crank roughness. You will sheer the piss out of the oil. Spun bearings are in your future.