Coolant temp vs. oil temp - high RPM and load

[BobFout]

While reading my operator's manual, high RPM and heavy load are only forbidden with respect to a cold engine (less than 160F coolant temp), nothing stated about oil temp.

The engine design allows the coolant to be warm very quickly, well before the oil even reaches 120F (the coldest it will display in the cluster).

This is counter what "we" are told about waiting for the oil to be warm before driving briskly. Does anyone have any insight on this?

 

[DoubleWasp]

Was it Lexus and BMW that actually had the computers hold the redline to about 3000-3500 rpm until the oil temps were above a certain temp?

 

[Brybo86]

I think that is on newer BMW with digital gauges

 

[rslifkin]

Generally I consider coolant temp to determine when it's safe to load it up fully (high manifold pressure or low vacuum) and oil temp to determine when high revs are safe (which happens after coolant is warm, typically).

On a turbo engine, I'd tend to wait until the oil is warm before getting it significantly into boost, for the sake of the bearings in the turbos.

 

[Nate1979]

High rpm on cold oil could mean your oil filter is in bypass.

 

[Shannow]

It's been posited by a member that he's seen many engines fail due to that on the track, but no evidence forthcoming.

I don't see too much of an issue with it, as the higher viscosity will be providing greater film thicknesses in bearing areas (bearing and piston skirts).

Could lead to higher oil consumption as the thicker oil in the rings could have the rings surfing over a greater volume.

Aforementioned filter possibly being in bypass could be an issue. Typically not, but a particle or two in the wrong place can score a bearing (countered by greater oil film thickness 'though).

Oil will be operating below the temperatures that the additives kick in, which shouldn't be a problem with an already established tribofilm.

Sequence IV, the wear test is purposely chosen to be an oil temperature of around 150F, as that's the sweet spot between viscosity dropping and additive function )on fresh engine parts too mind you).

More RPM will heat the oil quicker then idling, as the engine is doing work against the oil.

If I have to pull out and gun it on a semi warm engine, I'll have zero hesitation. I'll typically hold revs at 2,500 -3,000 RPM to help with oil warmup while I leave town, or the power station site.

 

[bbhero]

I've used your idea about using a lower gear early on with a very cold motor to help it warm up quicker. It does work very well to assist in getting the car up to operating temp much quicker. Keeping rpm between 2-3k. I'm glad my car has a shift mode that makes this very possible. This is a very good idea.

 

[Shannow]

 

[SHOZ]

Hyundai limits boost on their turbos motors until 150f or so. The OEM oil temp sender on my Genesis Coupe is up on the head by the cam solenoids.

I have the OEM sender reading and one I added immediately after the filter. There is also an oil/coolant heat exchange the filter mounts to.

Up to 140f the oil filter temp sender is the highest. After 140f it is the OEM sender in the head that reads highest.

 

[Bamaro]

Originally Posted By: BobFout
While reading my operator's manual, high RPM and heavy load are only forbidden with respect to a cold engine (less than 160F coolant temp), nothing stated about oil temp.

The engine design allows the coolant to be warm very quickly, well before the oil even reaches 120F (the coldest it will display in the cluster).

This is counter what "we" are told about waiting for the oil to be warm before driving briskly. Does anyone have any insight on this?

The manual is simply trying to extrapolate the oil temp by relating it to water temp since there is no temp sensor on the oil. IOW, if water temp is 160, oil temp must be above a certain threshold temp.

 

[MarkM66]

Originally Posted By: DoubleWasp
Was it Lexus and BMW that actually had the computers hold the redline to about 3000-3500 rpm until the oil temps were above a certain temp?


My sophisticated 2004 Pontiac Vibe does that. Won't go over 4k rpm until there's enough temp. Not sure what set temperature is.

 

[BobFout]

Originally Posted By: Bamaro
Originally Posted By: BobFout
While reading my operator's manual, high RPM and heavy load are only forbidden with respect to a cold engine (less than 160F coolant temp), nothing stated about oil temp.

The engine design allows the coolant to be warm very quickly, well before the oil even reaches 120F (the coldest it will display in the cluster).

This is counter what "we" are told about waiting for the oil to be warm before driving briskly. Does anyone have any insight on this?

The manual is simply trying to extrapolate the oil temp by relating it to water temp since there is no temp sensor on the oil. IOW, if water temp is 160, oil temp must be above a certain threshold temp.


There is an oil temp sensor.

 

[Gasbuggy]

My Cadillac hits full engine temp much much much sooner than oil temp. I usually wait until I'm over 120-130 before WOT.

 

[Jetronic]

well, the manufacturer of my car's engine states you are good to go as soon as the coolant gauge starts moving, so that's 120°F.

I wait at least until the coolant has reached normal operating temps. I'm more worried about uneven expansion of the aluminium head vs cast iron block putting stress on the head gasket than I am about the oil viscosity/temperature.

It takes at least 20 miles more (vs coolant at operating temp) to get the oil in the gearbox and engine up to temp (at normal speeds) which is when I start seeing the lowest fuel consumption.

My old car had an oil temp gauge, there I waited until the oil was 175°F and the oil cooler thermostat was open before really going at it.

 

[turtlevette]

When I ran my buick gn at bandimere, I made quarter mile passes dead cold. The times were much better on a cold engine.

 

[OVERKILL]

Originally Posted By: DoubleWasp
Was it Lexus and BMW that actually had the computers hold the redline to about 3000-3500 rpm until the oil temps were above a certain temp?


Mine had a variable redline on the tach that moved as the oil and coolant warmed up. It didn't stop you from rev'ing into that area though, it was just a guideline. That may have changed on newer ones.

 

[DoubleWasp]

Originally Posted By: turtlevette
When I ran my buick gn at bandimere, I made quarter mile passes dead cold. The times were much better on a cold engine.


While good for the performance of the engine, it is not as good for the longevity of an engine.