Best oil for new GM Direct Injection Engine

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Originally Posted By: Durango
My brother has the new GM engine for his Cadillac CTS and it has more power than my 08' Impala SS with the Corvette engine!!!!! For a V-6 that is impressive to say the least. His dealership uses Castrol "Syntec" instead of the Mobil 1 that is GM's standard. On my Impala SS the dealership uses Chevron products instead of Mobil 5000 for dino and their synthetic version for the Corvette's.

I guess each dealership options to use their own as they see fit.
Anyone know what the GM part number is for the over the counter oil/standard?

Durango

Let me guess. Was it the Martin Automotive Group?
 
Direct Injection engines generally suffer 2 problems that port injection engines don't have to the same degree.

First is fuel dilution in the oil as some designs get more fuel down into the lower part of the cylinder where it gets by the rings and into the oil. This is hard on oil - so at least get a quality oil analysis that includes Fuel Dilution readings after a 5K run on Synthetic.

Second is carbon deposit buildup on intake valves. With no fuel/air mix flowing through the intake ports, detergents in the gas can't clean the intake valves. So if an oil is more volatile, oil vapors will get sucked through the PCV and passed through the intake ports where it cooks onto the valves. This cannot be detected in oil analysis. Some say good synthetics that are tolerant of heat will be less prone to valve deposits. Others who have studied this problem have gone to Bio-based oils (RLI for example) which in particular DI applications cut the valve deposit buildup significantly.

Do some searching.... there are lots of discussions on the topic.
 
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Thanks jesbo for the explanation. I'm hoping my VW Passat doesn't suffer too badly from the 2 problems mentioned. YIKES!!!
 
All this seems to beg the question of whether DI is really the great thing that it's being made out to be. I'd rather trade some ultimate performance for the peace of mind of knowing that my engine was not constantly trying to trash itself.
 
Originally Posted By: The Critic
Originally Posted By: Durango
My brother has the new GM engine for his Cadillac CTS and it has more power than my 08' Impala SS with the Corvette engine!!!!! For a V-6 that is impressive to say the least. His dealership uses Castrol "Syntec" instead of the Mobil 1 that is GM's standard. On my Impala SS the dealership uses Chevron products instead of Mobil 5000 for dino and their synthetic version for the Corvette's.

I guess each dealership options to use their own as they see fit.
Anyone know what the GM part number is for the over the counter oil/standard?

Durango

Let me guess. Was it the Martin Automotive Group?



The Critic,

If you mean Martin Cadillac in the west L.A. area then your right on!

Durango
 
Originally Posted By: WGermany
Thanks jesbo for the explanation. I'm hoping my VW Passat doesn't suffer too badly from the 2 problems mentioned. YIKES!!!


DI is really good from a fuel economy perspective as it can improve mileage by as much as 15% over port injection because of the improved control of fuel/air mix

To add to the discussion, in europe manufacturers can program the DI fuel systems to stratify the fuel mixture as its injected into the engine, placing a leaner mixture in the lower part of the combustion chamber and a richer mixture near the plug to aid ignition. The mixture burns top-down evenly, and less fuel gets into the oil. Also, its more fuel efficient as overall you have a leaner mixture. The downside is the production of more NO2 emissions.

In the US, emissions requirements dictate that the DI fuel systems be programmed to use a more uniform (aka rich) mixture to keep the NO2 levels down. The byproduct being more fuel dilution.

So if you are driving a DI car in Europe, fuel dilution may be less an issue.

The carbon deposits on the valves issue is more difficult to deal with. Keeping the oil separators in good condition and PCV systems clear may help. Diesel engines have used DI for many years and I haven't heard of valve deposits being a big issue, so I don't know why it is any different with gas engines. May just be specific to certain engine designs. More research needed. :)
 
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Originally Posted By: ekpolk
All this seems to beg the question of whether DI is really the great thing that it's being made out to be. I'd rather trade some ultimate performance for the peace of mind of knowing that my engine was not constantly trying to trash itself.


I've been out of the loop for a while. Have they realized any mpg improvements from the higher compression ratios of some DI engines?
 
Originally Posted By: BuickGN
Originally Posted By: ekpolk
All this seems to beg the question of whether DI is really the great thing that it's being made out to be. I'd rather trade some ultimate performance for the peace of mind of knowing that my engine was not constantly trying to trash itself.


I've been out of the loop for a while. Have they realized any mpg improvements from the higher compression ratios of some DI engines?


I bought my 535i because of the combination of twin turbos, DI, and higher compression (though I'd say compression ratio is not that high). The 3.0 L engine is rated 300 HP with 300 ftLbs Torque, but some say its closer to 325 HP stock. Ive gotten nearly 30 MPG in straight highway driving with 3 adults and luggage, using cruise control with the A/C going. SO in my case I'd say yes - a well designed DI engine should give improved fuel economy.
 
I don't think there was much mpg improvement, but more power with the same mpg. We are getting well above the advertised 17 mpg city. We are getting 19 mpg city. I'm also hoping to get better than the 24 mpg highway rating. This is done with regular 87 unleaded which is great considering the high compression ratio. There are a few luxury Crossovers that have slightly lower compression but recommend premium unleaded and get less mpg.

So far this engine is one of the best running I have owned. It is literally whisper quiet.
 
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Originally Posted By: jesbo
May just be specific to certain engine designs. More research needed. :)


Valve deposits are well documented in VW and Audi engines. They are also seen now with regularity in BMW and even Porsche engines. DI engines are relatively new. As the cars get more mileage on them people see the deposits. Like the other day when I was told by a BMW delear employee that a 335i's valves was choked up badly at 50k miles. It's more widely seen in the V12 that has been DI longer as I understand it.

Yes we definitely need more research but for VW/audi we know really well how fast the deposits accumulate and even know some good techniques to deal with it (I listed them earlier in this thread). RL_RS4 has lead the way in discovering these deposits.
 
Originally Posted By: lonestar
To the question, “what the NOACK Volatility means and why it's important”. In a non DI engine the gas passing over the intake valves helps keep them clean and aids in “washing off” vaporized oil. In a DI engine fuel does not pass over the intake valves and thus vaporized oil will deposit on the valves. There is a pic somewhere on BITOG of a VW / Audi DI head after 7X,ooo miles and the valves are caked with deposits. If not corrected this will lead to messing up the valve seats as well as the valves.


How do you clean the intake valves of a DI engine? Presumably you can't just use a fuel injector cleaner to help them because the fuel doesn't go over the valves. Do you need to tear the engine apart?
 
Originally Posted By: wallyuwl
How do you clean the intake valves of a DI engine? Presumably you can't just use a fuel injector cleaner to help them because the fuel doesn't go over the valves. Do you need to tear the engine apart?


Remove a vacuum line while the engine is running and use SeaFoam or Amsoil's Power Foam. Allow the vacuum line to suck it into the intake manifold. It will clean the valve as it enters the combustion chamber.
 
Ingest the cleaner through the vacuum back into the intake in a mist/atomized form. Obviously not possible in daily driving so a maintenance and mitigation routine is your best option. If you are willing to risk or combat risking your warranty then there are probably more effective methods. Beware of all the internet/arm chare advice on the subject. Conventional maintenance will most likely be of minimal use.
 
Originally Posted By: Nederlander75
Ingest the cleaner through the vacuum back into the intake in a mist/atomized form. Obviously not possible in daily driving so a maintenance and mitigation routine is your best option. If you are willing to risk or combat risking your warranty then there are probably more effective methods. Beware of all the internet/arm chare advice on the subject. Conventional maintenance will most likely be of minimal use.


Do you really think, that baked on deposits will be removed by a quick spray (no scrub) of a chemical? Unlikely. The only way to truly clean valve deposits on a DI engine is to manually R/R the manifold and hand scrub the deposits off.
 
Originally Posted By: RamAir5
Valvoline Synpower has one of the lowest NOACK #s of a 5w30 oil... not counting Amsoil. PP 5w30 has a NOACK # of 12.5 while Synpower 5w30 has a # of 10.5.


Amsoil shows that Synpower has a Novack % of 13%!!! That's way to much for the DI engine. PP, Mobil 1, Redline and Amsoil are the only ones with a Novack% under 11.13%. PP is 11.13%, Mobil 1 8.23%, Redline 7.84%, and Amsoil is 6.9%

I am currently running the Amsoil ASL in my DI GM engine (Camaro) and it has used no oil and is running great. I will get a UOA after I change it again.
 
Originally Posted By: Jehartley
PP is 11.13%, Mobil 1 8.23%, Redline 7.84%, and Amsoil is 6.9%



As I recall Redline 5W30 has a NOACK # of 6%
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