Oil Pressue Warning during HPDE?
09-10-2013, 06:41 PM
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Oil Pressue Warning during HPDE?
I ran my first HPDE at Road Atlanta last weekend. Temps in the 90's and made four runs Saturday. My Audi is a 2002 A6 27t. High track speeds with pretty good g-forces coming out of turn 7 I got the oil pressure oil can light on the after lunch runs. Came off the track and checked oil and it was always full up. I am running Mobile 1 5w30 and of course bouncing off of redline a few times each run. I really think it is the combination of high temps, high revs, and g-force in the turns that made it come on. After is settles down I didn't get the light again even on the trip home (3 hours). Oil Temp gauge showed about 275 after a fast run typically runs about 225 in normal driving. Radiator temp always stayed in the center. I really think it may be that I need an oil pan with baffles in it or maybe even a heavier weight oil. Has anyone else had a similar problem?
09-11-2013, 04:30 AM
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5W30? In a turbo car on a hot track? There's your problem - the owners manual doesn't even suggest 5w30 for street driving under hot conditions. But more importantly, 30wt (~10-11 cSt) wont hold up to turbos under track use in anything.
I wont go into oil 101, you can search on "oil" and my signame for that, but do you understand oil, how it changes with temperature, and what the viscosities mean? In general thin oils flow well, especially cold. Thick oils hold up to shear, and resist flow (good pressure) when hot. On the track you are seeing extreme conditions (for a stret car) and always want something thicker. The trade-off with thick oil is that you simply should not run the motor beyond a super idle until it gets some temperature in it.
Furthermore, a 0w40, 5w40 and 10w40 will NOT have the same performance at hgih temps. Look at the specs. You simply cannot make a stable, wide-viscosity oil, period. So the simplest change is to use 10w40. Most have an HTHS ~4 and a cSt around 15, at 100 degC.
Turbos are particularly demanding because: 1 they have hgih output per unit of capacity; 2) the turbos get red hot and 3) those red hot turbos are spinning at 50,000 rpm and cooled by oil, which must not sludge in the bearing. I suspect some of yours did. This is how turbos die.
minimum 5w40 - and a good synthetic with high HTHS and minimal VII adders.
Preferred - 10w40 or 15w50, both of which, despite the numbers, have a much higher hot cSt
In my track car and even in my Audi when it ventures on track, i either do an oil change to thicker oil, or, if i'm cheap, i'll drain 50% and refill that with thick (15w50, 20w50).
That's really quite dangerous to your bearings.
Grant
I wont go into oil 101, you can search on "oil" and my signame for that, but do you understand oil, how it changes with temperature, and what the viscosities mean? In general thin oils flow well, especially cold. Thick oils hold up to shear, and resist flow (good pressure) when hot. On the track you are seeing extreme conditions (for a stret car) and always want something thicker. The trade-off with thick oil is that you simply should not run the motor beyond a super idle until it gets some temperature in it.
Furthermore, a 0w40, 5w40 and 10w40 will NOT have the same performance at hgih temps. Look at the specs. You simply cannot make a stable, wide-viscosity oil, period. So the simplest change is to use 10w40. Most have an HTHS ~4 and a cSt around 15, at 100 degC.
Turbos are particularly demanding because: 1 they have hgih output per unit of capacity; 2) the turbos get red hot and 3) those red hot turbos are spinning at 50,000 rpm and cooled by oil, which must not sludge in the bearing. I suspect some of yours did. This is how turbos die.
minimum 5w40 - and a good synthetic with high HTHS and minimal VII adders.
Preferred - 10w40 or 15w50, both of which, despite the numbers, have a much higher hot cSt
In my track car and even in my Audi when it ventures on track, i either do an oil change to thicker oil, or, if i'm cheap, i'll drain 50% and refill that with thick (15w50, 20w50).
That's really quite dangerous to your bearings.
Grant
Last edited by Just Me; 09-11-2013 at 06:17 AM.
09-11-2013, 02:19 PM
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I advise against 5w50 or 5w60. The real number to watch is the range/lower number. e.g.: 5w60 = (60-5)/5 = 11. 50-15=25/15 = <2. That's a nice ratio. Scientifically precise? No. ROM estimate of value? Yes.
I even noted that point in my reply, above. Wide viscosity ranges such as 5w60 can only be achieved with viscosity index improver. These are not long term shear and temperature stable, and shear down. When that happens you have two problems:
1. you don't have a 60, or 50 any more
2. you now have sludge pre-products
If you are tracking a car, bite the bullet and put in thick oil, with a thick base number as well. To make it drivable - with caution,i use, here in the Northeast, a cocktail of 10w40 and 15w50 yielding 12.5w45. Or close.
When i ran the S6 at VIR for 3 days and then at Pocono i just dumped the existing stuff and put in 15w50.
For the $50, you get proper protection on your $10k+ motor. Do it.
Grant
I even noted that point in my reply, above. Wide viscosity ranges such as 5w60 can only be achieved with viscosity index improver. These are not long term shear and temperature stable, and shear down. When that happens you have two problems:
1. you don't have a 60, or 50 any more
2. you now have sludge pre-products
If you are tracking a car, bite the bullet and put in thick oil, with a thick base number as well. To make it drivable - with caution,i use, here in the Northeast, a cocktail of 10w40 and 15w50 yielding 12.5w45. Or close.
When i ran the S6 at VIR for 3 days and then at Pocono i just dumped the existing stuff and put in 15w50.
For the $50, you get proper protection on your $10k+ motor. Do it.
Grant
09-12-2013, 04:15 AM
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But for synthetics, it's the opposite. A synthetic 5W-40 is actually a 40 grade oil.
I even noted that point in my reply, above. Wide viscosity ranges such as 5w60 can only be achieved with viscosity index improver. These are not long term shear and temperature stable, and shear down. When that happens you have two problems:
1. you don't have a 60, or 50 any more
2. you now have sludge pre-products
If you are tracking a car, bite the bullet and put in thick oil, with a thick base number as well. To make it drivable - with caution,i use, here in the Northeast, a cocktail of 10w40 and 15w50 yielding 12.5w45. Or close.
When i ran the S6 at VIR for 3 days and then at Pocono i just dumped the existing stuff and put in 15w50.
For the $50, you get proper protection on your $10k+ motor. Do it.
Grant
1. you don't have a 60, or 50 any more
2. you now have sludge pre-products
If you are tracking a car, bite the bullet and put in thick oil, with a thick base number as well. To make it drivable - with caution,i use, here in the Northeast, a cocktail of 10w40 and 15w50 yielding 12.5w45. Or close.
When i ran the S6 at VIR for 3 days and then at Pocono i just dumped the existing stuff and put in 15w50.
For the $50, you get proper protection on your $10k+ motor. Do it.
Grant
Also, formula 1 cars uses very thin oil - a straight 10. And they spin up to 15K RPMs.
09-12-2013, 04:42 AM
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I dont have time to get deeply into it. But as to your statement about mineral being "lower number" base stocks with VIIs to achieve the higher number, and vice versa, neither is true. Both numbers, technically, are merely test results (test and grade) and a base stock is selected to balance the two. Note that the actual hot viscosity of a 0w40 and 10w40 will vary significantly.
While synthetics can better meet a range, the problem remains, and can be easily seen by looking at viscosity over time, or a read-between-the-lines of an MSDS. Since i have access to actual formulation data, i don't need to read between the lines.
Wide viscosity still require viscosity modifiers with synthetic base stocks, beyond a certain range (which varies by quality and type of base stock).
Note also that there really is no difference between synthetics and regular oils - they merely refer to the type and degree of refinement. The molecules will have less variation in a synthetic.
Grant
While synthetics can better meet a range, the problem remains, and can be easily seen by looking at viscosity over time, or a read-between-the-lines of an MSDS. Since i have access to actual formulation data, i don't need to read between the lines.
Wide viscosity still require viscosity modifiers with synthetic base stocks, beyond a certain range (which varies by quality and type of base stock).
Note also that there really is no difference between synthetics and regular oils - they merely refer to the type and degree of refinement. The molecules will have less variation in a synthetic.
Grant
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09-13-2013, 06:33 PM
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HPDE Oil Pressure
Thanks for the advice from everyone. It makes a lot of sense. I will go with thicker oil for the next HPDE. Changing the oil viscosity is a small price to pay for better protection and now I have a better understanding of what to do. Thanks again to all.
I ran my first HPDE at Road Atlanta last weekend. Temps in the 90's and made four runs Saturday. My Audi is a 2002 A6 27t. High track speeds with pretty good g-forces coming out of turn 7 I got the oil pressure oil can light on the after lunch runs. Came off the track and checked oil and it was always full up. I am running Mobile 1 5w30 and of course bouncing off of redline a few times each run. I really think it is the combination of high temps, high revs, and g-force in the turns that made it come on. After is settles down I didn't get the light again even on the trip home (3 hours). Oil Temp gauge showed about 275 after a fast run typically runs about 225 in normal driving. Radiator temp always stayed in the center. I really think it may be that I need an oil pan with baffles in it or maybe even a heavier weight oil. Has anyone else had a similar problem?
5W30? In a turbo car on a hot track? There's your problem - the owners manual doesn't even suggest 5w30 for street driving under hot conditions. But more importantly, 30wt (~10-11 cSt) wont hold up to turbos under track use in anything.
I wont go into oil 101, you can search on "oil" and my signame for that, but do you understand oil, how it changes with temperature, and what the viscosities mean? In general thin oils flow well, especially cold. Thick oils hold up to shear, and resist flow (good pressure) when hot. On the track you are seeing extreme conditions (for a stret car) and always want something thicker. The trade-off with thick oil is that you simply should not run the motor beyond a super idle until it gets some temperature in it.
Furthermore, a 0w40, 5w40 and 10w40 will NOT have the same performance at hgih temps. Look at the specs. You simply cannot make a stable, wide-viscosity oil, period. So the simplest change is to use 10w40. Most have an HTHS ~4 and a cSt around 15, at 100 degC.
Turbos are particularly demanding because: 1 they have hgih output per unit of capacity; 2) the turbos get red hot and 3) those red hot turbos are spinning at 50,000 rpm and cooled by oil, which must not sludge in the bearing. I suspect some of yours did. This is how turbos die.
minimum 5w40 - and a good synthetic with high HTHS and minimal VII adders.
Preferred - 10w40 or 15w50, both of which, despite the numbers, have a much higher hot cSt
In my track car and even in my Audi when it ventures on track, i either do an oil change to thicker oil, or, if i'm cheap, i'll drain 50% and refill that with thick (15w50, 20w50).
That's really quite dangerous to your bearings.
Grant
I wont go into oil 101, you can search on "oil" and my signame for that, but do you understand oil, how it changes with temperature, and what the viscosities mean? In general thin oils flow well, especially cold. Thick oils hold up to shear, and resist flow (good pressure) when hot. On the track you are seeing extreme conditions (for a stret car) and always want something thicker. The trade-off with thick oil is that you simply should not run the motor beyond a super idle until it gets some temperature in it.
Furthermore, a 0w40, 5w40 and 10w40 will NOT have the same performance at hgih temps. Look at the specs. You simply cannot make a stable, wide-viscosity oil, period. So the simplest change is to use 10w40. Most have an HTHS ~4 and a cSt around 15, at 100 degC.
Turbos are particularly demanding because: 1 they have hgih output per unit of capacity; 2) the turbos get red hot and 3) those red hot turbos are spinning at 50,000 rpm and cooled by oil, which must not sludge in the bearing. I suspect some of yours did. This is how turbos die.
minimum 5w40 - and a good synthetic with high HTHS and minimal VII adders.
Preferred - 10w40 or 15w50, both of which, despite the numbers, have a much higher hot cSt
In my track car and even in my Audi when it ventures on track, i either do an oil change to thicker oil, or, if i'm cheap, i'll drain 50% and refill that with thick (15w50, 20w50).
That's really quite dangerous to your bearings.
Grant
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