the coolant temp rise in the oil/coolant heat exchanger will be less, in that way it can accept more heat from the oil which will cool down further.
How hot is too hot for motor oil
- Thread starter tom in boise
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Craig, commonly these target temps are never (at least very rarely) met. They're just targets. When oil temp is 252°F = 122°C, I'd bet coolant is something like 230°C = 110°C at least no matter which target. There's a huge difference between ideal and real. Btw, due to heat and knock and timing, he should run the highest octane fuel available at hot summer hillclimbs.
A 20°C decrease just with 75/25 coolant mixture is unrealistic, even a 10°C decrease is hard enough to obtain without hardware modifications, but it might be possible. However a gain of 5 Kelvin/°C for both coolant and oil is still worthwhile and that's what I'd expect with 75/25 coolant mix under the same circumstances. Using the heater will help even further. If this does keep temps in the 230s°F/110-115°C I'd call this mission accomplished. That's within comfortable range of M1 ESP 5W-30 which he's going to use. Remember this is a short-time duty, the OP isn't going to run his car at these temps every day.
On a side note: This GTI has a fairly precise factory oil temp gauge, but it lacks an exact coolant gauge. The factory coolant temp gauge is notoriously sitting at 90°C/195°F as long as actual coolant temps are "within range". For reasons mentioned before (coolant temp targets inherently lead to fluctuating coolant temps, which would make drivers watching a true gauge get crazy) I understand this is necessary.
A 20°C decrease just with 75/25 coolant mixture is unrealistic, even a 10°C decrease is hard enough to obtain without hardware modifications, but it might be possible. However a gain of 5 Kelvin/°C for both coolant and oil is still worthwhile and that's what I'd expect with 75/25 coolant mix under the same circumstances. Using the heater will help even further. If this does keep temps in the 230s°F/110-115°C I'd call this mission accomplished. That's within comfortable range of M1 ESP 5W-30 which he's going to use. Remember this is a short-time duty, the OP isn't going to run his car at these temps every day.
On a side note: This GTI has a fairly precise factory oil temp gauge, but it lacks an exact coolant gauge. The factory coolant temp gauge is notoriously sitting at 90°C/195°F as long as actual coolant temps are "within range". For reasons mentioned before (coolant temp targets inherently lead to fluctuating coolant temps, which would make drivers watching a true gauge get crazy) I understand this is necessary.
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Even without variable coolant temp targets it would be very disconcerting to see true coolant temps which can easily and quickly vary with 10C/18F. That's why the dummy gauges have been around for 25-30 years
Hmmm. Multiple posters seem to interpret that I claimed a coolant concentration change would result in a 20C temp reduction - not sure why that interpretation is dominant, that's not at all what I said. I do completely understand that "target" isn't reality - my statements were all conditional because we have not seen any data on whether the cooling system is achieving target or how far from target it is. (e.g. I wrote *IF* coolant is at target temp, THEN turning on the heater won't help).
So, my thoughts put another way,
So, my thoughts put another way,
- IF coolant temp cannot reach target THEN I would absolutely expect that lowering concentration AND running the heater will help (permitting the heat exchanger to transfer more heat from the oil by increasing the temperature gradient between oil and coolant)
- IF coolant temp is reaching target THEN I don't know that changing concentration or running the heater will do anything
- IF the OP has any way of lowering the temperature target in advance of the run (like I can on my N55) THEN that would also help significantly. (cabin heat may play a role here, it could bring the coolant temp below target, even if the target can't be lowered prior to the run)
- IF neither of these avenues can lower temperatures AND the OP cannot modify in any way THEN a higher HTHS oil will likely help with engine protection but may make the temperature problem worse - worth a try but I'd recommend baby steps, not going straight to 15W40 from 0W20 (random example, I'm not saying that someone here actually recommended that)
- IF temperatures can be brought more under control THEN switching oils may not be necessary at all - the runs are 45-100 seconds, not 45-100 laps. Changing it more often and doing UOAs might be a good idea.
- Because the GTI has a mechanical water pump, at the conclusion of runs the OP may wish to elevate from idle to something like 1200 or 1500 to pump coolant through the system faster. I assume that with every temperature well above target, thermostats will be wide open and electric fans will be running on max trying to shed as much heat as possible. Even better would be coasting downhill in a lower gear at 2000-2500 moving through fresh cooling air with no fuel being burned at all. Of course, then the system will set the highest target temp again for "efficiency" and "pollution control" so it'll probably only get down to 110C before everything closes off again - then add cabin heater on top of that I guess. Finding a legal way to tell the ECU to set the lowest target (e.g. 85C) at all times would be immensely helpful. The oil might only rise to 110C during a run if it started at 85C - problem solved.
Coolant temperature should not be thought of a single value.
Heat transfer is proportional to temperature difference.
Water has greater capacity to absorb heat, higher heat capacity. In other words for the same energy input water temperature rises less.
So for the same cycle water stays cooler, and therefore heat transfer is improved.
If coolant temperature is monitored after radiator & before engine block all it tells you is the radiator is able to dissipate heat absorbed from engine/oil.
Hypothetically - for 50/50, engine oil temp is 250F, coolant temperature max is 220F.
For 90/10, engine oil temp is 250F, coolant temperature max may be 215F.
Heat transfer = Constant * (T2 - T1)
So heat transfer is improved by 35/30 = +16%
What this really means in a dynamic sense is that the oil would never have gotten to 250F with 90/10 and would have settled ~245F.
And furthermore if min temperature of the coolant was above design, IE: radiator couldn't keep up at 50/50, it now will have a better chance, and max temp would come down even further.
So to put it simply, higher water concentration must improve heat transfer. In every possible situation. Whether its enough to matter depends on many factors.
It clearly will matter here because oil temepratures are high. Whether its 1 degree or 10 is the question. I'd suggest you give at least 20/80 a try.
I think my hypothetical above is probably not that far from what you'd see.
Heat transfer is proportional to temperature difference.
Water has greater capacity to absorb heat, higher heat capacity. In other words for the same energy input water temperature rises less.
So for the same cycle water stays cooler, and therefore heat transfer is improved.
If coolant temperature is monitored after radiator & before engine block all it tells you is the radiator is able to dissipate heat absorbed from engine/oil.
Hypothetically - for 50/50, engine oil temp is 250F, coolant temperature max is 220F.
For 90/10, engine oil temp is 250F, coolant temperature max may be 215F.
Heat transfer = Constant * (T2 - T1)
So heat transfer is improved by 35/30 = +16%
What this really means in a dynamic sense is that the oil would never have gotten to 250F with 90/10 and would have settled ~245F.
And furthermore if min temperature of the coolant was above design, IE: radiator couldn't keep up at 50/50, it now will have a better chance, and max temp would come down even further.
So to put it simply, higher water concentration must improve heat transfer. In every possible situation. Whether its enough to matter depends on many factors.
It clearly will matter here because oil temepratures are high. Whether its 1 degree or 10 is the question. I'd suggest you give at least 20/80 a try.
I think my hypothetical above is probably not that far from what you'd see.
Good lord - this post is going all over. You are racing your car - run a 40W oil and send it like so many do all the time including race teams running these same engines in their VAG race vehicles. I would never run a 20W for this use even though it's perfectly fine to use for daily duties. I've tracked my Sportwagen with what is essentially the same engine (EA888 Gen 3 1.8) with regular run-of-the-mill 5W40 Euro oil. My oil temps were around 240 at VIR with sustained triple digits. My UOAs, while certainly showing the impact (more viscosity drop than normal over that change), didn't look bad at all. I wouldn't **** around with coolant blends but that's just me.
edyvw
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His environment is much more challenging. Altitude is involved and that is a game-changer. Boise, ID itself is around 2,700ft, which is not dramatic altitude, but I am not sure where he does his hill climb.
Here at High Plains Raceway close to Denver, 4,900-5,000ft altitude no EA888 is going to stay on track longer than 15 minutes without limp mode even in moderate temperatures. There is just no enough air to do effective heat transfer. Everyone in VW's has these issues here and modifications are required.
With a bit lower altitude there he might get away with diluted coolant and running the heat at full blast to prevent the engine to go into limp mode during the run.
edyvw
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The question is what does it to the engine, not oil. UOA will not show that until things go south.
Sorry, I didn't intent to assume anything, I just tried to avoid any misunderstanding to any reader where possible.
Agreed. However it's safe to bet at 122°C oil temp it's impossible the coolant is even close to 85°C. Something 110°C is much more likely. Due to the oil/coolant heat exchanger the delta can't get that huge. That's why it does exist. Obeserving coolant temps via OBD gear would be my next suggestion to the OP.
Craig, I understand you're saying that to help understanding, but since this is extremely unlikely or even impossible under the OP's hillclimb scenario, it could also lead to some misleading. However I'm pretty sure 25/75 mix will help to come little closer to the 85°C target. See Dave's post.
Agree, but it isn't that easy as it's on a BMW. Some aftermarket tunes might have this implemented, but they also add power and more power means more heat. Hard to not use the addional power on a hill climb.
Even IF the 25/75 coolant mix does somewhat lower oil and coolant temps (which is to be expected even if we don't know how big the drop will be) I'd definitely also go one step thicker > 5W-30 VW 504 00. The OP ordered M1 ESP 5W-30 anyway. There's no argument against this dual approach. I agree to just make a smaller step, and there seems to exist some consensus on that. Another one is, that 0W-20 isn't ideal in this case.
Same as above, I understand you're saying that to help understanding, but since this is extremely unlikely or even impossible under the OP's hillclimb scenario, it could also lead to some misleading.
Raise rev to 1500 rpm seems a good idea. Another one would be to open the hood and/or spray some water onto the radiator. I thought about coasting downhill, but rules may not allow to leave finish immediately. You're probably right with the target going back to "efficiency mode" (107°C). That sad, but coolant temp will be somewhat elevated anyway.
It didn't appear that way, don't worry.
Sounds like you haven't done much lately...old washed up geezer. (joking).
We can't leave the finish area at the top of the hill until the last competitor has come up. I normally park, open the hood and leave the engine idling to allow as much heat rejection as possible.
edyvw
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What is the altitude at the top?
It is 3200 feet
edyvw
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Oh ok. That is not excessive.
Oops, I thought we're talking some higher elevation. I'm astonished it gets that hot at just 3200 ft.
I think that's a good strategy. Make sure the cooling fan is operational, that is a very common source of failure.
After the run I would definately run the heat full blast (AC off) if you can get out of the vehicle.
Because again in regards to heat transfer - its a dynamic situation so your starting temperatures will matter as well - ie: if your starting already in an over-heated state you basically have no chance during the run.
Maybe 1 other tidbit, make sure you're oil level is not at the min mark.
While it may make only a small difference the volume of oil can play a roll and the difference between min and max marks could give you more room to work with.
I'm not sure in this case it would be advisable to run at the max, esp with inclines, but def not min mark.
No,
252 degrees is fine, not worth thinking about. Most people don’t know about oil temperatures because they don’t have gauges in their cars,
If you start pushing 270 degrees then you may have to do something about it.
252 is within an expected operating range
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Running a big thermostatically controlled oil cooler will help tremendosly, you will also add more oil volume. Running a new in warranty car at sanctioned race events is risky not only can you void your warranty but if you wreck you car your insurance will not cover the damage. There is a racing exclusion on all insurance policies (read your policy). Overheating your oil may be the least of your worries. While it may be dificult for VW to prove abusise it is very easy to deny your claim should an accident happen. You may want to rethink using a new car for these events, especially if you are still making payments on the vehicle.
100 deg ambient day,
Good advice - No payments on this one. Never finance fun. Technically speaking, this is not a race. It is a timed event on a public street, not wheel to wheel competition on a race track. But believe me, I understand the insurance co lawyers would find some fine print somewhere.
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