Synthetic over Conventional Oil????
Senior Member
Joined: 11-27-2007
Posts: 1,115
From: Austin, Texas
Here is a good summary of the Oil Life Calculation for conventional oil (same principal for synthetic, just longer life of course). http://www.goodwrench.com/_res/pdf/OLS1.pdf
Senior Member
Joined: 09-12-2009
Posts: 143
From: Charlotte NC
Obviously there has been a lot of debate back and forth on this topic.
I bought my HHR used with about 24,000 miles on it. It has been run on conventional 5W-30 for that period of time.
My Cobalt SS used only Mobil 1 full synthetic, as recommended by the factory. I do plan on switching the HHR over to that when the time for my next oil change comes.
Per my dealer's advice I have always used the Oil Life meter in the dash as a guide for when to change the oil. I usually let the meter run to between 33% and 25%, then change the oil. With my driving this usually works out to around 4000 miles.
I bought my HHR used with about 24,000 miles on it. It has been run on conventional 5W-30 for that period of time.
My Cobalt SS used only Mobil 1 full synthetic, as recommended by the factory. I do plan on switching the HHR over to that when the time for my next oil change comes.
Per my dealer's advice I have always used the Oil Life meter in the dash as a guide for when to change the oil. I usually let the meter run to between 33% and 25%, then change the oil. With my driving this usually works out to around 4000 miles.
Senior Member
Joined: 11-27-2007
Posts: 1,115
From: Austin, Texas
Maybe I missed this, but an interesting thing to know would be if the SS and the 2.2/2.4 have different oil life readouts for equivalent driving patterns since the SS requires (and assumes) synthetic (mainly due to piston cooling jets that will coke the underside of the piston if conventional oil is used). For example for 2.2/2.4 and mainly fwy miles, what is your 50% oil life mileage?
Platinum Member
Joined: 01-09-2007
Posts: 16,081
From: SE USA
Maybe I missed this, but an interesting thing to know would be if the SS and the 2.2/2.4 have different oil life readouts for equivalent driving patterns since the SS requires (and assumes) synthetic (mainly due to piston cooling jets that will coke the underside of the piston if conventional oil is used). For example for 2.2/2.4 and mainly fwy miles, what is your 50% oil life mileage?
Not sure about the 2.2 ??
Senior Member
Joined: 11-27-2007
Posts: 1,115
From: Austin, Texas
Regarding deposits on the underside of the piston, I noticed that on a motor I had apart that had been run on synthetics, the pistons were very clean where I was used to seeing at least a brown coloration if not actual carbon with conventional oil on other motors.
Platinum Member
Joined: 01-09-2007
Posts: 16,081
From: SE USA
c2vette-
Quality synthetics produce almost no ash. Unlike dino-oils which do..
The 2.0 Turbos come with Mobil 1 Full Syn to also protect the turbo.
ie: Question:
Does Mobil 1 0W-40 Make a Turbo Engine Susceptible to Coking?
With my previous stock engine '01 Miata I used nothing but Mobil 1 0W-40 with completely satisfactory results on the street and track for over four years. I have recently replaced that car with a very low mileage '04 turbo MAZASPEED Miata and am using the same 0W-40 Mobil 1 oil for street and track. However, I have been strongly advised by seemingly knowledgeable MSM forum gurus that use of an oil with such a wide viscosity range in a turbo powered car makes the turbo bearings subject to coking. I routinely see oil temps of 230°-260°F here in the Arizona desert and would appreciate your technical opinion re the coking issue and whether Mobil 1 0W-40 is the appropriate and best oil for my MSM for street and track combination use in very hot southern Arizona.
-- Richard Olsen, Green Valley, AZ
Answer:
We would recommend you use either Mobil 1 5W-30, which has demonstrated outstanding performance in the HONDA HTO-6 Turbo specification and is recommended for Honda RDX Turbo, or Mobil 1 0W-40. Your friends are correct - wide multigrades can sometimes contribute to deposits. However, in the case of the Mobil 1 formulations, this is not an issue since it is formulated with high Viscosity Index base oils. This means it does not require excessive viscosity modifiers like conventional oils with a wide range viscosities. Secondly, Mobil 1 0W-40 carries all the outstanding qualities of all the other Mobil 1 grades including outstanding turbo performance and high temperature stability.
Source: https://www.mobiloil.com/USA-English...ne_Coking.aspx
Quality synthetics produce almost no ash. Unlike dino-oils which do..
The 2.0 Turbos come with Mobil 1 Full Syn to also protect the turbo.
ie: Question:
Does Mobil 1 0W-40 Make a Turbo Engine Susceptible to Coking?
With my previous stock engine '01 Miata I used nothing but Mobil 1 0W-40 with completely satisfactory results on the street and track for over four years. I have recently replaced that car with a very low mileage '04 turbo MAZASPEED Miata and am using the same 0W-40 Mobil 1 oil for street and track. However, I have been strongly advised by seemingly knowledgeable MSM forum gurus that use of an oil with such a wide viscosity range in a turbo powered car makes the turbo bearings subject to coking. I routinely see oil temps of 230°-260°F here in the Arizona desert and would appreciate your technical opinion re the coking issue and whether Mobil 1 0W-40 is the appropriate and best oil for my MSM for street and track combination use in very hot southern Arizona.
-- Richard Olsen, Green Valley, AZ
Answer:
We would recommend you use either Mobil 1 5W-30, which has demonstrated outstanding performance in the HONDA HTO-6 Turbo specification and is recommended for Honda RDX Turbo, or Mobil 1 0W-40. Your friends are correct - wide multigrades can sometimes contribute to deposits. However, in the case of the Mobil 1 formulations, this is not an issue since it is formulated with high Viscosity Index base oils. This means it does not require excessive viscosity modifiers like conventional oils with a wide range viscosities. Secondly, Mobil 1 0W-40 carries all the outstanding qualities of all the other Mobil 1 grades including outstanding turbo performance and high temperature stability.
Source: https://www.mobiloil.com/USA-English...ne_Coking.aspx
Last edited by sleeper; Sep 25, 2009 at 10:57 PM.
Senior Member
Joined: 08-29-2007
Posts: 256
From: CenCoast California
Of course, when you email Mobil Oil, they're going to answer as they did, ie: use M1 5W30. Interestingly, the person at Mobil who responded seemed not to read all your question, ie: the part about needing a "street/track" engine oil. But, I digress...
First, let's understand "coking"--it is destructive distillation in a low/no oxygen environment. With the 2.0L DI Turbo in the HHR SS, a tremendous amount of heat is transferred from the turbocharger's turbine and turbine housing to its center bearing. This bearing is lubricated and cooled by oil fed to it from the engine's oil pump. The oil flows through the bearing and then back to the oil pan. As long as the oil is flowing, there is no "coking" because the oil moves the heat away from the bearing into the greater oil supply and then to the atmosphere.
When engine stops and oil flow through the bearing ends, the turbine and housing is still much hotter than the bearing and, with no oil flow, the temperature of the oil in the bearing skyrockets. If it gets hot enough for the oil to breakdown, the coking process begins and once enough of this coke accumulates to plug the oil passages leading to the bearing, the bearing fries and the turbocharger fails.
This is why, with turbocharged engines subjected to extreme duty, such as racing or any high load operation, it is unwise to shut the engine down immediately after the extreme duty has taken place. It's best to take a "cool off lap" under light load or let the engine idle for a while. Obviously, synthetic engine oils, which are more tolerant of very high temperatures, are a hedge against coking when the engine is shut down.
.
As for the 230-260°F nominal oil temperature, for a petroleum based oil, indeed that's high. For a PAO synthetic such as Mobil 1 it's on the "high side of normal". For an ester-based synthetic that would be optimum oil temperature.
My suggestion, if you run your HHR SS in street/track duty cycle and you're seeing nominal oil temperature of 230-260 with occasional spikes to 275, you need a better oil than Mobil 1 and, regardless of brand, I wouldn't use a 5W30.
I suggest an ester-based synthetic such as Red Line 10W30.
First, let's understand "coking"--it is destructive distillation in a low/no oxygen environment. With the 2.0L DI Turbo in the HHR SS, a tremendous amount of heat is transferred from the turbocharger's turbine and turbine housing to its center bearing. This bearing is lubricated and cooled by oil fed to it from the engine's oil pump. The oil flows through the bearing and then back to the oil pan. As long as the oil is flowing, there is no "coking" because the oil moves the heat away from the bearing into the greater oil supply and then to the atmosphere.
When engine stops and oil flow through the bearing ends, the turbine and housing is still much hotter than the bearing and, with no oil flow, the temperature of the oil in the bearing skyrockets. If it gets hot enough for the oil to breakdown, the coking process begins and once enough of this coke accumulates to plug the oil passages leading to the bearing, the bearing fries and the turbocharger fails.
This is why, with turbocharged engines subjected to extreme duty, such as racing or any high load operation, it is unwise to shut the engine down immediately after the extreme duty has taken place. It's best to take a "cool off lap" under light load or let the engine idle for a while. Obviously, synthetic engine oils, which are more tolerant of very high temperatures, are a hedge against coking when the engine is shut down.
.
As for the 230-260°F nominal oil temperature, for a petroleum based oil, indeed that's high. For a PAO synthetic such as Mobil 1 it's on the "high side of normal". For an ester-based synthetic that would be optimum oil temperature.
My suggestion, if you run your HHR SS in street/track duty cycle and you're seeing nominal oil temperature of 230-260 with occasional spikes to 275, you need a better oil than Mobil 1 and, regardless of brand, I wouldn't use a 5W30.
I suggest an ester-based synthetic such as Red Line 10W30.
Senior Member
Joined: 08-19-2007
Posts: 829
From: So.Cal.
Most if not many turbos today are also water cooled to reduce the risk of coking. Is the HHR SS water cooled? What oil is factory recomended? 5W30? 0W40? or?
I'm not a fan of Mobil 1. Had a bad experiance with it in my '85 Vette. Raced with Amsoil. Use castrol Syntec in my Vette, Hotrod and Maverick. I do use Mobil 1 in my HHR because it's easier to find at oil change shops and the wifes PT Turbo and Crossfire because it is what the factory recomended (sticker under the hood).
I'm not a fan of Mobil 1. Had a bad experiance with it in my '85 Vette. Raced with Amsoil. Use castrol Syntec in my Vette, Hotrod and Maverick. I do use Mobil 1 in my HHR because it's easier to find at oil change shops and the wifes PT Turbo and Crossfire because it is what the factory recomended (sticker under the hood).