Will GC increase or decrease gas mileage?

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It will make little if any difference. If you are currently running a very thick 50 weight or a very light 20 weight, you may see a little more difference. I think all the oil makeers say that the oil itself is only a total 2-3% factor in fuel economy, so a change in viscosity would only be a portion of that.
 
Compared to using an API/SM or ILSAC/GF-4 formulation in the SAE 5w-30 grade, it will probably reduce your fuel efficiency by a very small amount. We're talking 1%-2% here at most ....

The sole reason is that the HT/HS viscosity of this oil is 3.6 Cp, compared to 3.0-3.2 Cp for most other 5w-30 grades. On the plus side the GC/0w-30 provides the best valve train protection of any SAE 0w-30 or 0w-40 you can get at that price point.

Tooslick
 
Well the GC has been inside my Scion tC for about a week, haven't had much driving time as of late to monitor how my gas mileage is. Although I did fill up recently with Arco which usually knocks my gas mileage down a good 2 or 3mpg
 
When I switched my 02 SE-R Spec V from M1 0W40 to GC I noticed an improvement in mileage. Approx avg. of 2mpg better.
Mind you I'm using the M0502+ batch numbers. Gold GC!
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I log and calculate every tank. In my truck, I switched from Castrol start-up 5w-30 to GC 0w-30. The mileage has been consistent and the same.

JMH
 
YMMV, but in my 2002 Subaru Impreza TS

M1 0W-30 (API SL) 24.5 MPG average
GC 0W-30 (API SL) 22.5 MPG average

Mine is only one data point on the information superhighway... feel free to add your own data point!
 
have run 4 10000mile oil samples so far. Two with M1-one Amsoil-and the last with GC. I average 42/45mpg. Toward the end of the Amsoil and the GC 10000mile run my milage had taken a noticable drop of 1to2+mpg only to be back to normal as soon as the oil change was made. Both the Amsoil and GC had thickend after the 10000mile run where the M1 had not. But the M1 showed a larger amount of iron where the Amsoil and the GC had not. 98 Suzuki Swift 1.3l
 
I dropped 4-5 mpg in comparison to M1 0w-30 or 5w-30. From my readings on this board the people who do the best with this oil are those with American cars or German cars. The ones who report most of the MPG drops are 4 cylinder Japanese makes.
 
Well, I noticed a drop in mileage with Mobil DC from the dealer for the 1st oil change. I then went to GC and had no change in mileage, but it was also the same time winter gas was coming out. I am now with RP 10w-30 and still getting the same mileage.
 
I noticed no change in mileage in my wife's Civic when I went from Mobil 1 Trisynthetic to Royal Purple 5w30 to GC 0w30. All three oils showed identical MPG numbers. She only gets about 23 MPG (city driving, combined with her lead foot)
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Ditto.

I noticed no change in mileage when I went from Mobil 1 5W30/10W10 to GC, and from GC to 0W40 Lubro Moly (now) in my 4-cylinder B16A2 Civic.
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quote:

Originally posted by JHZR2:
I log and calculate every tank. In my truck, I switched from Castrol start-up 5w-30 to GC 0w-30. The mileage has been consistent and the same.

JMH


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How did that Castrol Start-up do in your truck? Just curious because I felt it was a marketing gimmick from jump..
 
quote:

Originally posted by Patman:
I noticed no change in mileage in my wife's Civic when I went from Mobil 1 Trisynthetic to Royal Purple 5w30 to GC 0w30. All three oils showed identical MPG numbers. She only gets about 23 MPG (city driving, combined with her lead foot)
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Patman,every morning on the way in to work someone passes me like a complete maniac,racing from light to light in mulberry Civic.He's either slamming the gas or the brakes LOL.

One day i'm gonna blow the doors off of him
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