What determines how quickly an oil heats up?

[KOUPATROOPA]

Please excuse if this doesn't come out as easily to comprehend as it is in my head.

I am curious what determines how fast each individual oil heats up to optimum operating temps?
I mean does 0w cycle faster and therefore heat up faster than say a 5w or 10w?

Again please excuse my ignorance and lack of detailed explanation lol. I also did a google search but I think I am not phrasing my question right because google isn't helping much.

Thanks in advance for any info.

 

[Rand]

engine design, and usage.

 

[gpshumway]

It's actually a pretty complicated energy balance problem. If it's cold enough for the PRV to be open a thin oil will circulate at a greater flow rate through the engine, but a thicker oil will experience more frictive heating and will dwell on the hot parts of the engine longer.

Overall the individual engine design and how it's driven has a lot more to do with how fast it heats up than which oil you use. Anecdotally, my WRX with its heavy duty oil (currently M1 ESP 5w30) heats up dramatically faster than my Civic with water-thin M1 0w20.

I've looked pretty hard, I've never been able to find specific heat capacity numbers for particular oils, just reference book numbers for generic "motor oil" or "30wt oil" or some such. That tells me they're all pretty close.

 

[nepadriver]

Quote:
I am curious what determines how fast each individual oil heats up to optimum operating temps?



Thermometer?

 

[KOUPATROOPA]

Haha, that determines the temp of the oil not which oil heats up faster lol.

Thanks for the info guys.

 

[Jim Allen]

KOUPATROOPA: Is there some context to your question? If so, that might help us give you a better answer.

Yep, it really varies according to the engine, operational situation and the lubricant. I have been running oil temp gauges for years now on a couple of different engines. Ambient temp is the biggest factor in most cases I know about, as it controls the rate of temp rise as well as the peak operating temp. On warm (75-85F) days, the oil in my 5.4L Ford stabilizes at 180-190F after about 10+ miles of continuous operation and a low to medium load (stead 60 mph cruise). At the same operational situation at 25F ambient, it will barely reach 160 in that time. Given enough running time, it may get pretty near the warm weather temp but won't quite reach it.

This aspect can vary according to the individual engine, it's power density, whether it has an oil cooler, by oil capacity etc. Overall, if you need to know, job one is to install an oil temp gauge. A few engines have a sensor built into the engine that can be read by the PCM and if so, you may be able to read it via a device that connects to the OBDII test port

Increase the engine load at any ambient temp and the rate of rise also goes up as well as the stabilized temperature. Ditto for increase ambient temp.

I think heavier oil definitely effects both the rate at which the oil temp rises and the peak temps (at any load) but it's not hugely significant within the range of oils an engine might be spec'ed for. My engine is spec'ed for 5W20 but for a few years as an experiment I ran 10W30. I didn't see any significant differences in how fast the oil warmed up but I did see higher peak temps at any given load by about 5-10 degrees, which I attributed to fluid friction. None of this was significant IMO, just worth noting.

I've never tested 20W50 in an engine rated for 5W20 but I usually run 10W30 in a diesel also rated for 15W40 and I see lower oil temps by about 8 degrees in that truck.

My older diesel truck has a water-to-oil oil cooler. During warmup, the coolant warms the oil and brings it to a more efficient operating temp quickly, which is an efficiency advantage. Water and oil temp will equalize quickly.

 

[LotI]

Originally Posted By: Rand
engine design, and usage.

Displacement and material...the 4.2l all-Al engine warms up much faster than the 1.6l Fe-block engine even though the big motor holds 2 more quarts of oil and almost double the coolant. It's tough waiting for heat in the MINI when it's -14F outside!

 

[Ken2]

Koup, think of how the oil lubricates while it is warming. The specified oil for your engine, or maybe a lower "W" grade, will lube better before it is fully warmed--maybe 0W-30 instead of the recommended 5W-30, for one example. Automotive engines are made to get going with cold oil. Just take it easy. The oil may never reach its full summer operating temperature due to the cold air over the oil pan and the outside of the engine block--that's OK, that's part of normal winter driving. If full oil temperature was critically important, an electronic gizmo would be built in to limit engine operation until the oil was fully warmed.

 

[CATERHAM]

Originally Posted By: Ken2
The oil may never reach its full summer operating temperature due to the cold air over the oil pan and the outside of the engine block--that's OK, that's part of normal winter driving. If full oil temperature was critically important, an electronic gizmo would be built in to limit engine operation until the oil was fully warmed.

Actually getting oil temp's up to at least the low normal temp's of 80C or so is important if you want long engine life.
If you never do as can be the case with short trips in the winter, the AW additives will never get activated.

As for the OPs question, which heats up faster a 5W or 10W oil?
The question is moot because if the engine is cold enough for that to theoretically make a difference, the poor lubrication qualities of the 10W oil on start-up is a price you don't want to pay. The lighter the oil is on start-up the better, no ifs no ands no buts.