Worst gas mileage with GC

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I have a 03 SAAB 9-3. I have used SAAB turbo oil (Mobil 1 0W-30 LL) the last three oil changes. I decided to switch to GC for this 5,000 miles. SAAB calls for 0W-30 for this engine.

I was getting 29.5 mpg all the time. I now get 27 mpg with GC. Is this because GC is almost a 40 weight? I know SAAB is dumping their own turbo oil do to price. I might use Mobil 1 0W-40 or 0W-30R for a little bit more next time.

Thanks
 
quote:

Originally posted by Finklejag:
... Is this because GC is almost a 40 weight?...

Yes. Mobil1 0w-30 has a HTHS of 2.99cP compared to GC's 3.6cP, so you're going to see a drop in gas mileage.
 
Other people seem to be reporting all kinds of stuff when using GC . Rough idle and noise are other examples.
I'm fixing to run that oil in my wife's Corolla.....I think I might tweak it a bit for smoother operation.
 
I am running GC in my 98 4.6 f150 right now, and when I first put the oil in, I noticed an increase in gas mileage, but after about 1000 miles it must have thickened up a bit because I noticed a decrease in gas mileage. Now it has leveled off, but I am still noticing a decrease in fuel mileage over my 5w30 mobil1.

I think its a good oil though. I have about 3k on this oil, and i just checked it today and it looks as clean as the day I poured it in. I'm going to run it for about 6k then take a UOA and see how I did.

JH
 
I ran GC in my Audi 1.8T and i got a average of 28mpg on the highway. (65mph). The car is rated at 26mpg on the highway.
 
quote:

I was getting 29.5 mpg all the time. I now get 27 mpg with GC. Is this because GC is almost a 40 weight? I know SAAB is dumping their own turbo oil do to price. I might use Mobil 1 0W-40 or 0W-30R for a little bit more next time.

Thanks [/QB]

It seems to be that GC jumps around quite a bit depending on engine and driving.

The Mazda V6 we have went from 21-22 hiway mpg using M1 0w-40 to 23-24 with GC.
 
GC in my LS engines (02 Suburban and 04 Corvette ) has been one of the best oils I have ever had in there .... I think there's a lot of BS about GC floating around
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That 29.5 mpg is at 80 mph. I set the cruise at 80mph for my 40 mile trip to work. I will run a UOA when I dump in 5,000 miles.
 
quote:

Originally posted by Alex D:
GC in my LS engines (02 Suburban and 04 Corvette ) has been one of the best oils I have ever had in there .... I think there's a lot of BS about GC floating around
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Alex D,

I think this is one of the nicest things you have ever said...
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Guys the difference in mpg between a 30 Weight and a 40 is about 1-2%. I will buy that the difference between a light 30 and a heavy 30 is up to 0.6 mpg on a 30 mpg car. There are other factors involved here on both the gains and the losses.

Gene
 
quote:

Originally posted by Last_Z:
Other people seem to be reporting all kinds of stuff when using GC . Rough idle and noise are other examples.
I'm fixing to run that oil in my wife's Corolla.....I think I might tweak it a bit for smoother operation.


Used this in a friend's '02 Corolla and she reports an increase of about 2-3mpg over the previous dino oil. Noise is down quite a bit and the oil looks brand new at 7500 miles.

Which brings up a question for the group. She's due an oil change but doesn't have the money to do it right now. I know, it's only $30 or so to do a change with GC, but the money is tight right now (ex is WAY behind on the child support). The oil looks as clean as it did when it went in. Could I just do a filter change and top-off and let it go? She's at 8K on the oil and 89K on the car.
 
quote:

Originally posted by simpleguy_68:

quote:

Originally posted by Last_Z:
Other people seem to be reporting all kinds of stuff when using GC . Rough idle and noise are other examples.
I'm fixing to run that oil in my wife's Corolla.....I think I might tweak it a bit for smoother operation.


Used this in a friend's '02 Corolla and she reports an increase of about 2-3mpg over the previous dino oil. Noise is down quite a bit and the oil looks brand new at 7500 miles.

Which brings up a question for the group. She's due an oil change but doesn't have the money to do it right now. I know, it's only $30 or so to do a change with GC, but the money is tight right now (ex is WAY behind on the child support). The oil looks as clean as it did when it went in. Could I just do a filter change and top-off and let it go? She's at 8K on the oil and 89K on the car.


simpleguy_68,

Much as I love the Green Nectar, unless she is expecting the money to come in soon, or you were to pull a sample and do a UOA (compounds the funds shortage) I'd change the oil even if she has to do an "interim" change with dino until she can get the funds for the SLX. (IF she lived close I would donate SLX to the cause.) What kind of driving miles are on the change? Does the motor have "issues?" I'm grasping here because I really think it needs to be changed.
 
Miles on the oil are primarily highway miles. She drives app. 30 miles one-way to work everyday. The motor has no issues: no leaks, no oil-burning, no unusual noises, etc.

I've thought of doing a change using the Supertech Synthetic as an interim. With the filter, this is less than $15 for her vs. over $25 with the GC. But like I said, this oil looks nearly perfect at 8K, much cleaner than the Amsoil in my truck.
 
quote:

Originally posted by simpleguy_68:
Miles on the oil are primarily highway miles. She drives app. 30 miles one-way to work everyday. The motor has no issues: no leaks, no oil-burning, no unusual noises, etc.

I've thought of doing a change using the Supertech Synthetic as an interim. With the filter, this is less than $15 for her vs. over $25 with the GC. But like I said, this oil looks nearly perfect at 8K, much cleaner than the Amsoil in my truck.


You can't go purely on looks (probably true about a lot of things). Maybe this motor and SLX are a perfect match and she could squeeze more miles out of it as she is putting "easy miles" on it. I'd just hate to have the oil reach its limit and go south along with her motor (the latter admittedly a long shot)...talk about financial woes!
 
I don't get it because i've noticed an increase in gas mileage with GC.

However, I am considering Motul's 0W20 for this winter. (hopefully it'll pass, and i'll stick with GC).
 
quote:

Originally posted by Asmodeus:
I don't get it because i've noticed an increase in gas mileage with GC.

However, I am considering Motul's 0W20 for this winter. (hopefully it'll pass, and i'll stick with GC).


Mon ami,

I believe you might need some good counselling!
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Don't get me wrong, I'm not considering recommending that she go out to 15k on the GC, but I don't have a problem telling her she can put off changing it till 10k. That'll give her another month or so till she has to worry about changing it.

Then again, she once went 8k on conventional dino
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Regarding Finklejag's original question, does anybody think that moving from Washington (sea level?) to Colorado (5,000+ ft?) has any impact on mileage? Does relative (or absolute) humidity have any effect on combustion efficiency & mpg?


simpleguy_68,
The short answer: swapping in a new filter now would easily take her out to 10,000 miles. I'd do one of three things if this Corolla were my car:
1) Assume that I used GC 'cuz it's as good as everyone says, so there should be no problem going a minimum of 10,000 miles on it.
2) Assume everyone's blowing smoke out their butts & switch to an oil I know can go that long, like Mobil 1.
3) Switch her over to a high-quality HDMO year-round, & get her onto 5,000 mile oil & filter changes for around $10/change.

Now, there are a few unknowns, like how much oil does the car hold, & is her commute a straight shot for 30 mi or is a lot of it in stop-&-go city traffic? Those answers might trend the GC changes down towards 10k mi rather than up towards 20k mi. Another plan might be to wait until 10k mi, then swap in a new filter, top up with more GC & go on to 15k. But this oil's too expensive (& too hyped here on BITOG) to use for only 8k mi intervals.


pscholte,
So what's the deal with GC? Is it truly some wunder brauen, or is it simply a pretender to the throne? Any good Group III oil should go 8k mi in a decent N/A engine.
 
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