Subaru Forester Owners Forum banner

Status
Not open for further replies.
21 - 40 of 47 Posts

·
Premium Member
‘14 FXTT; '15 Legacy FB25
Joined
·
1,017 Posts
as stated above, blue oil light = engine oil temp too cold. many people still drive with the blue light on until it turns off. no matter the weather or anything, i always let the Forester idle until the blue light is gone (longer in the winter, shorter or non-existent in the summer). i was also told by some Subaru tech's that the blue light is even more important for the turbo Forester XTs, which makes sense since cold oil and fluids going through a hot turbocharger is a recipe for disaster (which i believe is both liquid-cooled and oil-cooled)
The blue and red lights are for ENGINE COOLANT TEMPERATURE.
 

·
Premium Member
‘14 FXTT; '15 Legacy FB25
Joined
·
1,017 Posts
Yea I only said oil temp bc my blue light goes out when my OIL temp is 100. As I recall..oil temp leads coolant temp. And of course oil temp can get much hotter than coolant temp. I don't know if oil temperature is indicated on non XT's.

I did not realize that this light blinks red if the engine coolant is approaching overheating and solid red if it IS overheating.
I experience similar times for the blue light to go out, related to oil temp. IME, oil temp lags coolant temp. As I posted above, when our oil temp is around 100F, the blue light goes out...at a coolant temp of around 122F. The oil temperature eventually COULD exceed coolant temperature, because, even in XT's with oil coolers (cooled by the same coolant as in the rest of the engine and radiator) can't keep up with the input. The oil AND coolant coming out of the turbo will be a lot higher than the bulk temperature of each.
 

·
Premium Member
‘14 FXTT; '15 Legacy FB25
Joined
·
1,017 Posts
Here's a datalog to prove that oil lags coolant (at least for my '14 FXT). You'll note that they eventually become equivalent. Oil doesn't exceed coolant temp until 770 seconds into the log!!!

You can also see that it took me just over 3 minutes to reach a coolant temperature where the blue light would have gone out.

EDIT: can't upload .csv or .xlsx files here for some reason...here are some pics
 

Attachments

·
Premium Member
‘14 FXTT; '15 Legacy FB25
Joined
·
1,017 Posts
Print them as pdf, and then you can upload.
I think pictures prove the point. You guys don't need to sift through 50k cells to do what a .jpg will show in one slide. Please see the post above yours - I edited it to show pics of the applicable cells.
 

·
Registered
2019 Forester Limited
Joined
·
553 Posts
@gathermewool , How about a screenshot of the temperature plots? Edit: Never mind. Needed to refresh/reload the page to see you new info.

Inferring anything about lead and lag depends very much on temperature sensor location and which one you're reading. I'm not saying anything about your results, just something to be aware of.

On the 2019, oil temperature is measured by a single sensor near the filter, while two sensors are used to measure coolant temperature in separate locations. One near the water pump ("inlet engine coolant temperature sensor") and the other near the thermo control valve at the top of the engine ("outlet engine coolant temperature sensor"). The sensor near the water pump appears to read radiator outlet temperature, while the one near the thermocontrol valve appears to read the temperature of coolant leaving the engine. The diagrams are not precise enough for me to be 100% certain.

The 2019 radiator is bypassed when the car is cold, and the temperature near the water pump will just sit there until the control valve routes fluid to the radiator. In this case, oil temperature will certainly lead coolant temperature. The coolant sensor at the top of the engine responds quicker, although I couldn't say how fast relative to the oil sensor.

2018 and earlier Foresters lack a thermo control valve, so their measurements will be different than the 2019 during warm up. Once everything settles in (steady state), they should be similar.

All this makes me want to purchase a used/cheap android phone since iPhone's don't appear to have OBD apps to log things like this (and transmission temp). Not because I NEED to; I just enjoy this sort of thing. :geek:
 

·
Premium Member
2019 Crosstrek 2018 XT
Joined
·
13,608 Posts
Peak oil temperature (not what you read on the oil temp gauge) will always be hotter than water coolant its ALWAYS (the peak) closer to the "action" like turbo and wrist pin bearings. Just an engineering fact. I'll stop there ;)
 

·
Registered
Joined
·
5 Posts
On my 2019 forester, the blue coolant light shows up every time i start my car. for about 3 minutes.

it's hovering around 18C here in BC... so it's not that cold by any means. i never had this light on ever for my toyota prius.

Is this normal or do i have to get this checked?
My husband would add air conditioner stuff that’s in a can
 

·
Premium Member
‘14 FXTT; '15 Legacy FB25
Joined
·
1,017 Posts
Unfortunately, we don't have turbo outlet temperature or piston ring-pack outlet temperature indicators. My post has nothing to do with max vs max; I was responding to a post about the indications we CAN monitor...Let's not get wrapped around the axle here.

Also, where the oil is scraped off of the piston will undoubtedly see the highest temperatures in the engine, we should discuss bulk temperatures, because, well, we don't have the other data. We have what we have.

My husband would add air conditioner stuff that’s in a can
:unsure:

:ROFLMAO:
 

·
Registered
2013/14 2.5i-L CVT
Joined
·
724 Posts
Modern engines (and oils) don't need to be idled until they reach temperature. Not only does this waste fuel, but it does nothing for the rest of the drive train. Getting transmissions, especially torque converters (CTs) warm asap is arguably just as important. This is why engine revs are higher while the CT+CVT are cold.
 

·
Premium Member
2019 Crosstrek 2018 XT
Joined
·
13,608 Posts
Modern engines (and oils) don't need to be idled until they reach temperature. Not only does this waste fuel, but it does nothing for the rest of the drive train. Getting transmissions, especially torque converters (CTs) warm asap is arguably just as important. This is why engine revs are higher while the CT+CVT are cold.
You can make a case for being able to get on the gas really aggressively at 150F or so. Oil is flowing and high load and heavier oil go fine together.
 

·
Premium Member
‘14 FXTT; '15 Legacy FB25
Joined
·
1,017 Posts
You can make a case for being able to get on the gas really aggressively at 150F or so. Oil is flowing and high load and heavier oil go fine together.
My cutoff is usually 140F oil temp, but, to be honest, I'm not going to let ANY temp get in the way of a safe merge into traffic. My '14 FXT and '15 Leggy work for me, NOT the other way around! If they fail prematurely I'll find some other make of vehicle that won't...or has a longer warranty period (I'm looking at you, Kia)
 

·
Registered
Joined
·
16 Posts
On my 2019 forester, the blue coolant light shows up every time i start my car. for about 3 minutes.

it's hovering around 18C here in BC... so it's not that cold by any means. i never had this light on ever for my toyota prius.

Is this normal or do i have to get this checked?
when you say everytime, do you mean just the cold start? or it comes up even after the coolant is hot?
 

·
Registered
2001 Forester S auto
Joined
·
231 Posts
Wow, besides all the safety recalls with newer Foresters, you guys have to deal with "normal" illuminated dashboard lights about coolant temperature too??? Call me antiquated or whatever you must, but I'll keep my weird looking first generation Foz. Thanks.
 

·
Registered
2015 Forester2.5i Premium CVT
Joined
·
1,019 Posts
^ Talk about adding apples and salmon and coming up with a box of rocks! As in many, many cars, there are indicator lights to show the coolant temperature range. Subaru's are more informative than some: Blue/off/flashing red/red to indicate cold/normal/getting hot/too hot. Combined with the oil temperature digital readout, it's a comprehensive and immediate picture of the state engine temperature. I like this setup much better than the simple uncalibrated coolant-temperature gauges I had in most of my earlier cars. (An arc divided into three sections.)

What that has to do with recalls, I can't begin to imagine. FYI, according to this article...

5 Car Brands with the Most Recalls—and 6 with the Fewest

...between 2014 and 2018 Subaru was one of the six least recalled brands in America. But every brand has significant numbers of recalls these days, as cars get more complex and their safety systems more sophisticated, so I'm glad I have a Subaru. Which tends to be more pro-active, more willing to voluntarily recall and fix things for free without being forced by the government, even when they're not specifically safety-related.
 

·
Premium Member
‘14 FXTT; '15 Legacy FB25
Joined
·
1,017 Posts
Wow, besides all the safety recalls with newer Foresters, you guys have to deal with "normal" illuminated dashboard lights about coolant temperature too??? Call me antiquated or whatever you must, but I'll keep my weird looking first generation Foz. Thanks.
I honestly can't tell if you're being sarcastic. Just in case you're not:

There's nothing easier than a little light to tell instantly what's going on. I used to think differently until I realized that coolant gages with an analog needle are just dummy gages that are easy to ignore for most people. A light going out or coming in (especially if it's red and blinking) should catch your eye more than a needle making its way over to the red stealthily.
 

·
Registered
2001 Forester S auto
Joined
·
231 Posts
I honestly can't tell if you're being sarcastic. Just in case you're not:
I'm pretty serious. There's a bigger picture here. Instead of relying on lights, people who all drive the lastest Foresters should still check the fluids almost daily. Unless you can clarify objectively, the whole concept of a dashboard light staying illuminated after the vehicle is in motion, seems completely asinine, because the vehicle could have been better serviced at it's origin when parked and the engine is cool. Would you rather be pulled over on a busy freeway trying to diagnose a cooling system problem because the light told you so? Not I. Seems to me that if this feature were to tell the driver about a faulty thermostat, then it's a good idea, however, they should have deigned the light to illuminate WHEN the problem arises... instead of vice versa.
 

·
Registered
2001 Forester
Joined
·
880 Posts
Unless you are driving a vehicle that is running Straight 30W oil with a carburetor, there is never any need to warm-up an engine. If you feel you need to warm-up any car today then you are following this myth warm-up to get the engine flowing to all parts of the engine it's a stupid myth.....


1. 0W or 5W oils are more than thin enough to flow freely except maybe in -40C in Alaska, Yukon, etc...If you think it will not flow unless warmed up, then don't drive it, leave it shut off, you are only damaging the engine if you think the oil is not flowing......0W/5W oil flows pretty darn good
2. Carburetors were also the main reason for warm-up, they never worked well until the engine was fully warmed up. Engines with carburetors needed a warming valve on the intake, this warming valve was controlled by a coolant sensor. It's purpose was to inject/duct warmed air into the air filter, without this valve engines would stall or mis-fire or stumble badly. So with fuel injection, why do you need to warm-up the engine.
 

·
Registered
2015 Forester2.5i Premium CVT
Joined
·
1,019 Posts
Unless you can clarify objectively, the whole concept of a dashboard light staying illuminated after the vehicle is in motion, seems completely asinine, because the vehicle could have been better serviced at it's origin when parked and the engine is cool.
The blue light conveys exactly the same information as a gauge pointer that hasn't reached the first increment. Should there be no gauges, or should they somehow be rendered invisible when nothing is happening? You are making no sense.

You seem to be stuck on the idea that it's a light. What would you prefer as an indication that coolant has not yet reached normal operating temperature?
 

·
Registered
2001 Forester S auto
Joined
·
231 Posts
You seem to be stuck on the idea that it's a light. What would you prefer as an indication that coolant has not yet reached normal operating temperature
I'm not really stuck on the idea that it's a light. You're missing the point. On the contrary, critical dashboard lights should definitely illuminate when there is a powertrain problem, not when THERE ISN'T ONE. In due course, if that elaborately programmed electronic firmware should ever fail despite necessary repairs and maintenance having been done, then an owner may disregard it entirely, while secondary cooling system issue can take root and possibly destroy the engine. The purpose of having TWO coolant temperature probes in the plumbing is so the user/driver could possibly be alerted to a cooling issue before the computer is told by it's probe. It seems to me like Subaru did away with that conventional wisdom and replaced it with their belief that the less the driver knows, the better. I am just dumbfounded by how much it behooves people these days to take a split second to glance at a needle on a scale when they are driving. Is it really that much of an inconvenience?
 
21 - 40 of 47 Posts
Status
Not open for further replies.
Top