Oil Teperature v Engine wear graph?

[mechanicx]

Originally Posted By: expat


Well I'm not so sure about that.[/quote]

Ever fitted an oil temperature gauge? [/quote]

Well if you have some numbers of the coolant temperature rising much faster than the oil temperature share them.

Keep in mind if you have temp guage in the sump vs a temp guage in the water jacket, that's not really fair comparision. You would need an oil meaurement closer to engine location.

 

[mechanicx]

This is kind of funny because I quickly googled this off another site and it references this site. It don't know that it address oil warm up time vs coolant but it addresses oil temp vs coolant:

Quote:
http://www.bobistheoilguy.com/...29178
Zoz, Steve, et. al., Engine Lubrication Model for Sump Oil Temperature Prediction
SAE Paper 2001-01-1073

At 60 mph oil is ~ 20C hotter than coolant, at 4000 rpm it is 50C hotter
"on the average, the Oil Sump temperature is always 1.2 to 1.43 times higher than the coolant temp. "

I wounder exactly how this applies to old Q.

It is important that the oil get to 212F to boil off all the condensation fast.

But that means you maybe driving with water in the oil for the first 5-10 miutes. Why you don't rev and engine until the oil is hot!!!!!!!!!!!!!

 

[Gary Allan]

Quote:
Why would the coolant heat up faster than the oil?


Tremendously larger contact surface area to the combustion process. ..higher rate of forced circulation..

Oil will heat some due to pressure loading ..otherwise it's a fraction of the flow that hits the piston underside and the cylinder walls. It can't be heated traveling over the head until the jackets are heated. Keep in mind that the oil, at whatever rejection rate it has at the moment, is bleeding off heat constantly. At any sustained state, the oil (assuming no forced cooling of any type) temp is expression of thermal excess that's not being rejected by the radiator or traveling out the exhaust (losses ignored).

 

[mechanicx]

well I'm not going to belabor the point. The cylinder head is usually aluminum and conducts heat around the water jackets to wear the oil contacts, too. The coolant is being circulated even with the thermostat closed. If oil took longer to heat up it would seem it would also run cooler than the coolant temperature after warm up as well but it doesn't.

I don't have any hard facts or numbers, but until I see them this is what I think. My original point wasn't really about oil warm up anyway, but that until coolant warms up there is going to be more cylinder wall wear almost regardless of oil temp.

 

[Gary Allan]

Oil temp will vary with load. You can figure this by how much pedal you're applying at any given speed.

A car towing @ 60 mph will have a higher oil temp than one unloaded at the same speed. The difference (among a few - but this being the most important imo) is the btu's being processed through the engine via the combustion cycle.

That's why it works out to an almost "square" time/mile equation. It's about as broad as it is long. It will probably take you 20 minutes to reach the mileage of normalized oil temp ..and 20 minutes will work out even under lower load than highway speeds. There you're processing more rpm's per mile, albeit at lower cylinder pressure.

Oil temp will vary from vehicle to vehicle due to air flow and pan composition and area. Mine hung around 215F-220f depending on load. Coolant temps in the same engine were about 185-195F with a 195F thermostat.

You've got a few complications on viewing oil temp. Just the rules of heat exchange make it difficult. I think the highest temp I saw on my minivan was around 225F when it was loaded with passengers @70mph. It wasn't that much lower empty at the same speed (about 213-218)

If one is measuring bulk oil temp, I don't see an issue with the drain plug as a place for the sensor. The pickup is right there. That's the location where the engine sees the oil first. There will surely be temps higher of varied levels to make that composite. Most of us don't have multiple points from which to measure.

 

[mechanicx]

I suppose the coolant can warm up faster than oil, then the oil eventually gets hotter than the coolant temperature depending on load. I still think though that if coolant temp is low, wear will be higher even if oil temps are over 180 or whatever. That's what happens when you run a cooler thermostat basically. I just wonder how hot the oil needs to be at a minimum and how long that takes past coolant warm up?

 

[expat]

I hear that 170F can be considered the low end of optimal for oil temperature, as Gary says, on a day of moderate ambient temperature, that can take 20 min. +- 5 min.
On my car, that is a typical, normal, highway temperature. Prolonged speed in excess of 70mph will raise that to 190f-200f
Add in a few hills on a hot day, 220f.

 

[Gary Allan]

Watercraft use cooler thermostats. I don't quite understand why, but they run frequently @ WOT and the oil temp is still up there (220F+ is common). They wear out a whole lot sooner than passenger car engines (identical engines) but it's due to being at WOT. If any life extension could be achieved with just a thermostat change, they would surely do it. It would be hard to find enough road to only operate your passenger car @ WOT. I guess if you only climbed 8% grades and towed or coasted it down the other side and turned around.

That's not to say that I reject the notion of cooler meaning more wear. It's just a situation of qualifying the environment. Watercraft engines are in the most demanding load scenario possible most of the time. They're pushing the oil temps to most sensible sustained limits.

 

[fsskier]

Watercraft do not generally have pressurized cooling systems, and the boiling point of the coolant is thus much lower. Hot spots in the heads would produce localized boiling, liming up and subsequent failure. Each 1 lb increase in cap pressure raises the boiling point about 3 degrees F - cars commonly use 14 lb pressure caps with their 190 degree thermostats.
Some outboards use dual stage cooling, idling at 160 degrees and dropping back to 140 degrees at large throttle openings.

 

[Gary Allan]

Even on exchanged engines? Makes sense on raw water cooling. I'm just curious.

 

[expat]

I would guess marine engines proberbly do just as many revolutions in their life (or more) than an equivalent Automobile engine.

But what about Air cooled engines? How do they fare in terms of wear?

 

[Gary Allan]

Originally Posted By: expat
I would guess marine engines proberbly do just as many revolutions in their life (or more) than an equivalent Automobile engine.

I would say that they probably process the same amount of fuel as a comparable automobile engine. They compress engine life into a shorter operational time frame.

Quote:
But what about Air cooled engines? How do they fare in terms of wear?


Good question.

 

[fsskier]

"How about exchanged engines?" I do not know what they use for thermostats, that is a question for the salt water boaters!
We do not see a lot of salt water here in the midwest!!

Yes, car engines in boats often live a much shorter life than in cars, after 1500 hours many are shot, with lots of bore wear. Cars usually cruise with just a touch of throttle, boats are pulling hard at all times, and may be run at full throttle for extended periods of time.

 

[roadrunner1]

the reason for cooler thermostats in raw water cooling systems is that mineral deposits will form in the casting if heated much over 160`, all of the marine engines i have had raw water cooled have had 140` thermostats.
closed cooling systems, properly sized, should have the same thermostat as one in automotive use (180`-195`) because the operating conditions are equal, anitfreeze circulating through the block doesn't know how it is being cooled, whether air with a radiator, or marine applications, either heatexchangers or keel cooled

 

[expat]

The more I think about it, the more I suspect that those wear graphs were plotted by holding an engine (the whole engine) at a sustained low temperature, and measuring wear at that temperature.
The coolant or the oil, was just the vheical for reading the engine temp during the test, the wear was generated by the metal components of the engine being 'miss matched' due to incomplete expansion stabilisation.
Preheating the oil or the coolant only may not (significantly) have an effect on wear until the total engine is warmed also.
Of course warming the fluids 'would' help speed the total warming.

What do you think?

 

[Gary Allan]

I'd love it if one of our Canadian members with a block warmer used it year round. It would take a long time in the testing, but one would think that if the fuel enrichment part of the warm up cycle was a significant contributor, that the bypassing of this state would show substantial improvement.

It would help if the user already had a year of UOA with only limited winter use. I say Canadian since they're more likely to have a block warmer. While many surfaces would also be warmed, there would be a big difference fro a 150F+/- cylinder wall/piston (perhaps) and the temp it reaches under combustion. Most of the thermal expansion curve is still intact. The oil would still be cold, but would warm somewhat quicker than usual.

It wouldn't be conclusive ..but should suggest the significance of corrosive wear in the scheme of things.

 

[expat]

Our volunteer Fire and Ambulance do just that, the vehicles are plugged in (I believe) year round. Unfortunately I am NOT on good terms with those guys right now!

I have been thinking along the same lines as you re; start up oil dilution on cyl walls. That's why I was wondering about the possible benefit of UCL during cool weather (Perhaps added only during warm up, But what would that do to Cat life?)
Oil in gas works wonders in a Two Cycle engine!

 

[mitsuman47]

Originally Posted By: Gary Allan
I'd love it if one of our Canadian members with a block warmer used it year round. It would take a long time in the testing, but one would think that if the fuel enrichment part of the warm up cycle was a significant contributor, that the bypassing of this state would show substantial improvement.

It would help if the user already had a year of UOA with only limited winter use. I say Canadian since they're more likely to have a block warmer. While many surfaces would also be warmed, there would be a big difference fro a 150F+/- cylinder wall/piston (perhaps) and the temp it reaches under combustion. Most of the thermal expansion curve is still intact. The oil would still be cold, but would warm somewhat quicker than usual.

It wouldn't be conclusive ..but should suggest the significance of corrosive wear in the scheme of things.


I believe I remember seeing someone do that with a Jetta. But, I'm not able to locate it. They had 6 UOA's from what I can remember. 3 with and 3 without a block warmer. The results were significantly better with the block warmer.

I'll keep looking...


Edit: Found it. It was an oil pan heater. And it looks like the Fe was the only thing that improved.

Jetta with oil pan heater

 

[Gary Allan]

I dunno. While I'm generally adverse to adding anything to oil as a rule, I have no such feeling about fuel. Fuel blenders (I imagine) are probably more into drivability issues than they are engine wear reduction issues.

 

[mechanicx]

Originally Posted By: expat
The more I think about it, the more I suspect that those wear graphs were plotted by holding an engine (the whole engine) at a sustained low temperature, and measuring wear at that temperature.
The coolant or the oil, was just the vheical for reading the engine temp during the test, the wear was generated by the metal components of the engine being 'miss matched' due to incomplete expansion stabilisation.
Preheating the oil or the coolant only may not (significantly) have an effect on wear until the total engine is warmed also.
Of course warming the fluids 'would' help speed the total warming.

What do you think?


I agree with that. I think the coolant and engine cylinders need to be warm for wear to be low.