Why you should run synthetic oil in your GDI engine
I don't dispute that millions of engines have done just fine over the years running conventional motor oil with regularly scheduled oil changes. But here is my take on the story and why the old school wisdom no longer applies to direct injected engines..
A little background:
The MK3 Focus uses Ford's GDI (Gasoline Direct Injection) engine. What this means is that the fuel injectors have been moved inside the combustion chamber of the engine. This improves power and provides improved fuel economy by allowing more precise control of the fuel/air mixture by the computer. Ford also increased the compression to 12:1 on the GDI engine.
Any negative aspects of Direct Injection and what does this have to do with my oil choice?
The main problems with Direct Injection are carbon fouling of the intake valves, fuel dilution of the oil and oil blow by contaminating the intake valves. (Ford claims to have solved the oil blow by problem with their variable valve timing algorithm)
Why you should still follow Ford's oil change interval
If you are tempted to lengthen your oil change interval on the GDI engine, don't. Even if you use the most advanced Group V base stock synthetic oil, there may still be fuel dilution of the oil due to the nature of the GDI engine. Fuel dilution increases volatility and reduces lubricating capacity. The only way to remove this is with regular oil changes following Ford's schedule.
So why run a synthetic oil in a GDI engine if conventional oil is almost as good and much cheaper?
Volatility and viscosity. Some synthetic oils offer a very low volatility (NOACK) What this means is that less oil vapor is given off at operating temperature than a higher volatility conventional oil. That oil vapor can't be vented to the atmosphere. Because of emissions requirements, it is routed back to the intake manifold through the PCV valve. Those oil deposits start to collect on your intake valves and you may soon experience loss of power, rough idle, stumbling on acceleration and engine misfire codes. Once the carbon is that bad, the only way to remedy it is to manually clean the valves. This requires the removal of the intake manifold and possibly the head, (very expensive) So it is in your best interest to run the lowest volatility synthetic oil in your Focus that you can buy. Pennzoil has also done research on the carbon fouling issue and they believe that running a narrow viscosity span oil such as 5W-20 (that Ford recommends) is beneficial. This is due to the fact there are less viscosity index improvers in 5W-20 vs 5W-30 etc.
Can't i just run a top tier gas such as Shell V-Power to keep my intake valves clean?
I recommend top tier gas but it will do nothing to clean your intake valves because the fuel injectors are inside the combustion chamber and the detergent fuel never washes over the valves. Only air and oil vapor from the PCV valve passes over the valves and this is why it is critical to use a low volatility synthetic oil in your GDI engine. Remember it is not a matter of having sufficient lubrication for engine longevity. A conventional oil could also provide a long service life. Running a low volatility synthetic is a matter of trying to prevent carbon fouling of the intake valves.
What about a catch can?
(An aftermarket reservoir that is plumbed in to the PCV return line to catch oil before it reaches the intake manifold)
I don't recommend it for several reasons:
1. Dozens of these have become available; quality varies and there is little evidence they are truly effective. Even if they work as advertised, they only catch liquid oil, not the oil vapor that contaminates intake valves. The only unit that can catch oil vapor is the Mann-Hummel Provent. It contains a replaceable filter. It is expensive and requires periodic maintenance.
2. It is illegal to alter the emissions system.
3. It may void your factory warranty.
4. The 2.0 GDI engine already has an oil separator from the factory. The Ford engineers cleverly routed the separated oil back to the crankcase so there is no maintenance. But the factory oil separator has the same limitation as a catch can: it can only separate liquid oil. Vapor still passes through to the intake manifold.
What synthetic oil is best?
Here is a chart of most of the major brand synthetics so you can compare. This chart lists data for 5W-30 oil but it will give you an idea of which synthetics have lower NOACK volatility scores.
http://pqiamerica.com/March2013PCMO/Marchsyntheticsallfinal.html
I run Pennzoil Ultra 5W-20 which sports a NOACK score of 5. Ultra 5W-30 has a NOACK of 6.4 and Ultra 10W-30 has a NOACK of 4.8. These are the lowest NOACK scores of all the major brand synthetics and almost as low as much more expensive boutique oils such as Amsoil. Here is the full product data for Pennzoil Ultra:
http://www.google.com/url?sa=t&rct=...UpD0Jofc2QXrwIDgBQ&usg=AFQjCNEeIraAVj7a_G0pmOBnFu6RznS3Wg&bvm=bv.51773540,d.b2I
Anything else I can do to keep my intake valves clear of carbon?
Do an "Italian tuneup" Take your car out on the highway and get your revs up to 4000 and hold it for 20 minutes. The intake valves will get very hot and this combined with high intake velocities will burn off light carbon deposits.
The lower the volatility of the oil, the less oil vapor will be returned to the intake manifold.
wavsine
Picture of BMW Direct Injection engine after 53,000 miles of oil vapor passing over the intake valves. Second picture is after disassembly and manual cleaning.
I don't dispute that millions of engines have done just fine over the years running conventional motor oil with regularly scheduled oil changes. But here is my take on the story and why the old school wisdom no longer applies to direct injected engines..
A little background:
The MK3 Focus uses Ford's GDI (Gasoline Direct Injection) engine. What this means is that the fuel injectors have been moved inside the combustion chamber of the engine. This improves power and provides improved fuel economy by allowing more precise control of the fuel/air mixture by the computer. Ford also increased the compression to 12:1 on the GDI engine.
Any negative aspects of Direct Injection and what does this have to do with my oil choice?
The main problems with Direct Injection are carbon fouling of the intake valves, fuel dilution of the oil and oil blow by contaminating the intake valves. (Ford claims to have solved the oil blow by problem with their variable valve timing algorithm)
Why you should still follow Ford's oil change interval
If you are tempted to lengthen your oil change interval on the GDI engine, don't. Even if you use the most advanced Group V base stock synthetic oil, there may still be fuel dilution of the oil due to the nature of the GDI engine. Fuel dilution increases volatility and reduces lubricating capacity. The only way to remove this is with regular oil changes following Ford's schedule.
So why run a synthetic oil in a GDI engine if conventional oil is almost as good and much cheaper?
Volatility and viscosity. Some synthetic oils offer a very low volatility (NOACK) What this means is that less oil vapor is given off at operating temperature than a higher volatility conventional oil. That oil vapor can't be vented to the atmosphere. Because of emissions requirements, it is routed back to the intake manifold through the PCV valve. Those oil deposits start to collect on your intake valves and you may soon experience loss of power, rough idle, stumbling on acceleration and engine misfire codes. Once the carbon is that bad, the only way to remedy it is to manually clean the valves. This requires the removal of the intake manifold and possibly the head, (very expensive) So it is in your best interest to run the lowest volatility synthetic oil in your Focus that you can buy. Pennzoil has also done research on the carbon fouling issue and they believe that running a narrow viscosity span oil such as 5W-20 (that Ford recommends) is beneficial. This is due to the fact there are less viscosity index improvers in 5W-20 vs 5W-30 etc.
Can't i just run a top tier gas such as Shell V-Power to keep my intake valves clean?
I recommend top tier gas but it will do nothing to clean your intake valves because the fuel injectors are inside the combustion chamber and the detergent fuel never washes over the valves. Only air and oil vapor from the PCV valve passes over the valves and this is why it is critical to use a low volatility synthetic oil in your GDI engine. Remember it is not a matter of having sufficient lubrication for engine longevity. A conventional oil could also provide a long service life. Running a low volatility synthetic is a matter of trying to prevent carbon fouling of the intake valves.
What about a catch can?
(An aftermarket reservoir that is plumbed in to the PCV return line to catch oil before it reaches the intake manifold)
I don't recommend it for several reasons:
1. Dozens of these have become available; quality varies and there is little evidence they are truly effective. Even if they work as advertised, they only catch liquid oil, not the oil vapor that contaminates intake valves. The only unit that can catch oil vapor is the Mann-Hummel Provent. It contains a replaceable filter. It is expensive and requires periodic maintenance.
2. It is illegal to alter the emissions system.
3. It may void your factory warranty.
4. The 2.0 GDI engine already has an oil separator from the factory. The Ford engineers cleverly routed the separated oil back to the crankcase so there is no maintenance. But the factory oil separator has the same limitation as a catch can: it can only separate liquid oil. Vapor still passes through to the intake manifold.
What synthetic oil is best?
Here is a chart of most of the major brand synthetics so you can compare. This chart lists data for 5W-30 oil but it will give you an idea of which synthetics have lower NOACK volatility scores.
http://pqiamerica.com/March2013PCMO/Marchsyntheticsallfinal.html
I run Pennzoil Ultra 5W-20 which sports a NOACK score of 5. Ultra 5W-30 has a NOACK of 6.4 and Ultra 10W-30 has a NOACK of 4.8. These are the lowest NOACK scores of all the major brand synthetics and almost as low as much more expensive boutique oils such as Amsoil. Here is the full product data for Pennzoil Ultra:
http://www.google.com/url?sa=t&rct=...UpD0Jofc2QXrwIDgBQ&usg=AFQjCNEeIraAVj7a_G0pmOBnFu6RznS3Wg&bvm=bv.51773540,d.b2I
Anything else I can do to keep my intake valves clear of carbon?
Do an "Italian tuneup" Take your car out on the highway and get your revs up to 4000 and hold it for 20 minutes. The intake valves will get very hot and this combined with high intake velocities will burn off light carbon deposits.
The lower the volatility of the oil, the less oil vapor will be returned to the intake manifold.
wavsine
Picture of BMW Direct Injection engine after 53,000 miles of oil vapor passing over the intake valves. Second picture is after disassembly and manual cleaning.
