Curley... Not trying to "bite your head off", just want to keep the facts out there for everyone and not the myth and lore. Please don't take offense and you have a nice day too!

Driving style and Knock Learn Factor actually have little to do with each other, other than a heavy foot (aka heavy load) can make knock more likely to occur. Fuel trims only deal with the system trying to stay on stoic AFR. That's got nothing to do with knock.

Catdaddy, good questions! I don't honestly know just how quickly the Knock Learn will average up or down vs. time or miles. It would be intersting to see. HPTuners can log the Factor, so the rate of change could be observed though.

 

Nope.
Our family is involved in aviation but I'm not a former flight engineer.

 

Any "5W30" is an "SAE5" viscosity at 0° F and a "SAE30" viscosity at 212°F.

The GM Ecotec four cylinder engine family is designed for an SAE30 engine oil when it's at 210° or so. The 5W part of the oil, aids in easier starts in extremly cold weather, ie: 0°F or colder and it aids in very slightly increasing fuel mileage when the oil temp is below 212 but above atmospheric.

In the early 1980s as a way to "kiss butt" to the Federal Government and as a way to incrementally increase the fleet average fuel econonmy of all its vehicles, with a few exceptions, GM has recommended 5W30 engine oils.

To make a multiviscosity 5W30 oil, Mobil Oil and other companies blend "viscosity index improvers" into engine oils. The "VI" improvers are what give petroleum-based and synthesized-hydrocarbon based oils their multi-viscosity properties, but VI improvers have no lubrication ability and they break down under very high temperature.

At higher oil temperatures, which a small four-cylinder engine without an engine oil cooler, such as an Ecotec, will sustain on a regular basis, a 5W30 is not as good an engine oil choice than a 10W30, because it has more VI improvers which can degrade lubrication. This is main reason I always suggest a 10W30 unless the duty cycle is regular operation in very cold weather.

As for what oil to use, well...that depends on how you drive your HHR and how much you want to spend.

The best engine oils, regardless of price, are ester-based synthetics. Red Line, the brand I use, is one of those.

The Mobil 1 brand is a large family of synthetic lubricants marketed by Exxon/Mobil Corp. The Mobil 1 engine oil distributed widely in North America is a synthesized-hydrocarbon-based synthetic, which is certainly better than a typical mineral oil, but not as good as an ester-based synthetic. Ester-based synthetics typically have very little or no VI improvers. Red Line 10W30 has no VI improvers. Red Line 5W30 has a very slight VI improver component which is much less than that of petro- and synthesized hydrocarbon based oils.

Bottom line on engine oil for your 2.2 or 2.4 Ecotec if the duty cycle is "normal".

Ok: factory-fill or equiv. petroleum-based 5W30.
Good: petro-base 10W30
Better: Mobil 1 10W30
Best: Red Line 10W30.

As for who really needs a 5W30? If you not just start, but operate your HHR in temperatures which are below zero most of the time, then you should use a 5W30 petro-based oil or Mobil 1. If I operated my HHR in weather that was zero or below quite often, I'd probably be using Red Line 5W30.

But....that's not the case. My HHR "lives" in southern California so I want better protection and lubrication at oil temperatures beyond 212°F, thus I use a 10W30 and an ester-based one at that.

I think ester-based synthetics are a better choice in extremely cold weather, too, as they do not have as much of a viscosity increase at temps below 32°F. I've run Red Line 10W30 in temps as low as -20°F. and have had no trouble with starting. This is because while it's an SAE10 at zero, it's still close enough to that at -20 that cranking RPM does not decrease much. Try that with a petroleum-based 10W30 and the results might not be as good.

 

My understanding of is that the system will select either the high-octane or low-octane tables and is not capible of "averaging" or picking some level of spark timing between those two.

The point "JoeR" makes about "speculation" is a good one. There's nothing wrong with speculation---as long as everyone who reads the thread knows the person posting is speculating on how the ECM sets spark timing but doesn't actually know how it works.

 

Hib, Good write-up on the oil. One of the greatest "challenges" for all is discriminating between advertizing hype and real fact. God help us all!

As for "Knock Learn Factor"... here's how HPTuners defines it:

"Knock Learn:
Knock Learn is a method the VCM uses to provide a longer term adjustment for fuel octane. If the VCM detects knock it will instantaneously reduce timing (Knock Retard) but will also modify the Knock Learn factor to affect the proportion the VCM uses to interpolate between the High Octane and Low Octane Main Spark tables. If no knock is detected over a reasonable period then the Knock Learn factor will slowly return to the High Octane table.

Main Spark Tables:
The VCM constantly looks up both High Octane and Low Octane spark tables and interpolates a value between the two tables based on the current Knock Learn factor. If the engine has been operating for a moderate time without any Knock Retard then Knock Learn is zero and the interpolation favors the High Octane table, if Knock has been detected then the interpolation will move towards the Low Octane table."

Hope that makes sense. I just hooked up to my HHR and logged the KLF. I had done extensive tuning for the supercharger, based upon using good 93 octane gas and the LNF is ZERO for me. Also note that I've spent a lot of time on a dyno tuning for max torque at normal cruizing speeds and loads. Even with the SC, I can get consistent 37.5 MPG or so on long trips.

There's just so many variables that it's hard to nail down accurate figures. Gas quality, octane available in your area, "winter blends", mandated E10 in some areas (like mine), driving habits, terrain, wind, temp conditions. Way too much to really nail things down for the most part.

GM has to write their calibrations to deal with all of the above. Consider that a "worst case" scenario and still meet standards. The 2.4 LE5 has high octane "recommended", NOT required. Given the relative costs of fuel at different octanes and the thermodynamic efficiencies due to the ECM calibrations, my (NOTE THIS>>>) "speculation" is that:

1. Overall fuel costs are almost a "wash" between gas octanes and MPGs in this engine. I think Snoopy did some good data that pretty much confirmed this.

2. Power level will be "somewhat" reduced with lower octane. GM even states ths. Now how noticeable this is is left to speculation.

 

Hey HIB, great write up on the oil...
I have been very confused ever since I bought my SS and had the GM6094 specification requirement.
I purchased some Valvoline Synpower 5W30 to use in my LNF and even contacted their technical dept who said it "Meets or exceeds the GM6094 specs", but have been afraid to use it as it is not on the GM approved list...
I see that the Red line is not listed as well, any idea of why that is?
Also, can you recommend any other ester based oils to use.
I think I am going to start running 10W30 now that I have a better understanding of how they get down to 5W30 rating

Thanks in advance,

 

I never realized how the learn function worked. I've been using 87 octane in my 2.4 even though 92 was recommended. I have used 93 octane for as many as 2000 miles with no mileage improvements, so reverted back to 87. Why spend the extra $0.20/gallon with no real improvements.

I did see a local station that says they have 100% gas (no 10% ethanol blend) at about $0.10/gallon more. I may try a tank full prior to taking off next week for a road trip, as I have seen a decrease in mileage since they started forcing the ethanol blended gas on us.

 

One of the claimed advantages of 5W30 oil over the thicker oils is supposed to be that it flows through the block galleys quicker to the various oiling points.My contention,and the reason that I don't like the 5w30 oils,is that if it flows TO the oiled areas quicker it also flows AWAY from them quicker too,which to my mind lessens protection on cold starts when the oil is mostly all in the pan.Hib,since you've done much research on oils and have a lot of data,am I off base in my belief or not?

 

Did we loose Hib?
I thought his explanations were very good and he put things into terms that I could understand.

I was curious to get his answer on other types of ester based oils and his thoughts on the need to meet the GM 6049 requirement....

 

Nope.
I'm still here. I just was away on a road trip for two weeks then had to spend a week back in the office "fighting fires" that started while I was away. I've also been busy posting to another forum site that deals with 4x4s about a tire test I conducted on my two-week trip. It was only this morning that I had a chance to get on here and read recent posts to this thread.

I need to keep reading and then I'll post some answsers to the oil questions.