Engine Oil Viscosity - wasted energy during warmup

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Couple of facts that people seem to have a hard time getting across lately, pertaining to warm-up, oil temperatures, and why OEMs are switching to lighter viscosities, and the Japanese penchant for higher VIs.

Here's a map of the energy input into heating the oil in the first minutes after start-up, taken from
warmup.jpg


https://edupediapublications.org/journals/index.php/ijr/article/download/925/875

In that 1.7L 4 cylinder engine, at cold start, the work that the rotating assembly is doing to the oil is 4KW, there's 4KW of heat, just due to viscous friction heating the oil (and consequently the block and coolant) in the first minutes...

That's where the lower KV40/Higher VI lubes are saving the manufacturers money in CAFE credits...and saving the end user fuel as well, obviously.

In a country where the majority of trips are less than 10 minutes, then it's clearly a winner.

And contrary to popular opinion, if you have a look at the 9 minute and onwards, the contribution to oil heat rejection is about evenly split between internally generated viscous friction, and that transferred to it through combustion.
 
That explains why Ford's 2.7L v6 ecoboost engine in pickup trucks uses an interesting dual-volume sump. Its probably there to let the oil warm faster before full mixing in the sump occurs.
 
Quote:
..Through the study, it is seen that, the cold start performance of the IC engine is poor at cold climate like Himalayan region..


Indeed.
 
Originally Posted By: DoubleWasp
Effect must be very insignificant. I've seen no change at all in fuel economy going from a 20 weight to a 40 weight.


That's not what the paper was about...the effect that you are talking about is 2-3%, and is there.

The paper is about what's happening during the warming phase, when the oil goes from a couple of hundred times the operational viscosity through to normal viscosity.
 
Originally Posted By: DoubleWasp
Effect must be very insignificant. I've seen no change at all in fuel economy going from a 20 weight to a 40 weight.


Ditto in my charger.

However I'm not a short tripper. If I'm starting a vehicle I'm going to do as much as possible as far as errands are concerned. And I'll plan my day so that I accomplish everything.
There is a grocery store 6 short blocks away in a mini mall that also contains a pharmacy and a bank. I'll walk to get what I need unless I'm needing to buy a ton of stuff.

I'm going to assume a short tripper may notice an increase in fuel consumption because it takes more heat to thin the oil. More drag means more fuel. Once you multiply that by umpteen short runs I'm sure it adds up.
 
I use 5w30. Would I notice reduced fuel consumption going to a 20? Would that difference overcome the higher fuel use of manual choke and fast idle when cold?
 
Originally Posted By: Olas
I use 5w30. Would I notice reduced fuel consumption going to a 20? Would that difference overcome the higher fuel use of manual choke and fast idle when cold?


no it wouldn't overcome all that. a 20 weight when cold is still several times more viscous than a hot 30 weight
 
Chucking M1 5W20 and M1 5W30 into a viscosity calculator gives 410 and 450cst respectively at freezing.

I doubt that you'd notice anything.
 
Originally Posted By: Clevy
However I'm not a short tripper. If I'm starting a vehicle I'm going to do as much as possible as far as errands are concerned. And I'll plan my day so that I accomplish everything.
There is a grocery store 6 short blocks away in a mini mall that also contains a pharmacy and a bank. I'll walk to get what I need unless I'm needing to buy a ton of stuff.

I'm going to assume a short tripper may notice an increase in fuel consumption because it takes more heat to thin the oil. More drag means more fuel. Once you multiply that by umpteen short runs I'm sure it adds up.


We've got two cars, and I alternate them over a month or two to drive to work.

Work car gets 3km of country town, then 18km of highway, and the reverse. Town car gets to stay in the 3km, and do groceries, kids to dancing...stuff.

The Caprice gets 21MPG (US) on work duty, and 14 on town duty.
 
Originally Posted By: Olas
I use 5w30. Would I notice reduced fuel consumption going to a 20? Would that difference overcome the higher fuel use of manual choke and fast idle when cold?

You might if you get a lab to run a bunch of tests for you, repeatedly. You or I will never notice in ourselves. It is there, of course.
 
Following on from this, the idea of using light load to more rapidly warm up the engine (rather than idle), and my Poohpooed "Italian Tune-up" thread where I can get the Caprice oil temperature to 135C by holding it in "2" at highway speeds.

http://ogst.ifpenergiesnouvelles.fr/articles/ogst/pdf/2013/01/ogst120033.pdf

Figure 3 shows the European warmup drive cycle, and Figure 4 a comparison of a regular IC engine, and a hybrid attacking the cycle.

Hybrid does (as they do) uses the engine harder in the early part of the cycle (if you've driven one, you'll know that they are straight into it), then has a period of electric only.

The initial hit, the metal, the water, and the oil all increase in temperature quite rapidly compared to the IC only.

Can duplicate the effect by holding the Caprice in "2" while I drive to the town limits in the morning...temperature gauge moves a lot facter.

Quote:
These results are consistent with the experimental resultsobtained by Trapy and Damiral [1]. Their study about theevolution of the engine oil temperature rate and its depen-dence on torque and speed show indeed that the oil warm-upis strongly dependent on the ICE speed but is almost notinfluenced by the engine torque.


Torque = load.
 
Ok. So if I used my manual mode in my Altima and kept in lower gears for say the first mile or two would warm it up much faster correct? Aka like keeping a regular automatic car in "2".
Which I could easily do.
 
yes, but it would also use significantly more fuel. that's ok if the intent is to get the cabin warm though, or you need to get heat into the engine before pressing on (to get the aw chemistry operational when really using the engine). But be aware that thermal expansion will happen at a different rate, I'm not sure how headgaskets like it.
 
Originally Posted By: Jetronic
no it wouldn't overcome all that. a 20 weight when cold is still several times more viscous than a hot 30 weight


Yes but a hot 30 weight is still thicker than a hot 20 weight. I'd be questioning the 20 weight's ability to provide the necessary lubrication at full operating temperature.
 
Originally Posted By: bbhero
Ok. So if I used my manual mode in my Altima and kept in lower gears for say the first mile or two would warm it up much faster correct? Aka like keeping a regular automatic car in "2".
Which I could easily do.


Yep, here's what Jaguar/Rover say about their tranny programming.

Quote:
In cold conditions, the transmission selects a lower gear to promote fast warm up and get the engine up to its efficient operating temperature as soon as possible.


It's a word doc.
 
Originally Posted By: Jetronic
yes, but it would also use significantly more fuel. that's ok if the intent is to get the cabin warm though, or you need to get heat into the engine before pressing on (to get the aw chemistry operational when really using the engine). But be aware that thermal expansion will happen at a different rate, I'm not sure how headgaskets like it.


I don't see how it would use "significantly more fuel", over the first say 10 minutes.

The load on the engine is the frictional load plus the load to move the car...the latter stays the same, the former is greater in the short term due to the work being performed against the oil.

There shouldn't be any material effect on the headgaskets.

Literature indicates that in this mode, an amount of the heat that is generated in the oil goes through bearings and blocks into getting the coolant up to temp.
 
Originally Posted By: bbhero
Ok. So if I used my manual mode in my Altima and kept in lower gears for say the first mile or two would warm it up much faster correct? Aka like keeping a regular automatic car in "2".
Which I could easily do.


I wondered about doing that, and the consequences, if any to an automatic transmission. I realize when it's very cold, an automatic doesn't lock up the TC until a certain temp is reached, [to warm the fluid, engine, and cc faster] but it's not holding a lower gear. I'm pretty certain it would not impact a standard transmission at all. An automatic otoh I'm not sure.
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