Gas mileage with German Castrol

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So I took a round trip from Ohio to North Carolina over the weekend. This would give me a good test of mileage with GC. On long trips, small variations in driving habits are more likely to get averaged out. Well, I'm happy to report that I set a new record, 33.8 mpg. My previous high was 33.4 with Castrol GTX 5w-30. I rarely exceed 32 with Synpower 5w-40. I do this trip often so the route is pretty similar. One thing that concerns me though is that gas mileage seems to have jumped up since this trip. Even on a couple local trips today, I set new records for mileage (14 mile highway trips). For example, I have neve gotten over 30 mpg before (even with GC!) from work to home and this evening I got 32.2! I had the same experience with GTX and I attributed it to thinning. But I highly doubt that the GC could have thinned this much given that it has shown to hold viscosity well in UOAs and I only have 1300 miles on the oil. Can anything else cause the mpg to jump like this?
 
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My mileage is up from <20 to 22.5. On-board trip computer is accurate to .1 mpg.
 
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Originally posted by VeeDubb: *-*- Well, I'm happy to report that I set a new record, 33.8 mpg. My previous high was 33.4 with Castrol GTX 5w-30. -*-*
IMO I have seen when a new oil seems to raise the MPG, it will either in time go up slightly or go down slightly with the miles. More often than not it will rise with the next two or so OCI. Keep track and let us know.
 

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I'm just sitting here waiting for psholtes reply.. [Big Grin] Make it a good one! [Cheers!] [Patriot]
 
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The only way to really tell if motor oil is responsible for an increase in fuel economy is to do a test under controlled conditions. You would need to use the same batch of fuel, the air should be the same temperature and humidity level, the exact same route would have to be taken, and the throttle position would also have to be controlled and be consistent. A double blind study would also be helpful. Anything less is really not a scientific study and not really accurate.
 
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Originally posted by GSV: I'm just sitting here waiting for psholtes reply.. [Big Grin] Make it a good one! [Cheers!] [Patriot]
LOL. Me too, I never get tired of statements concerning the Green Elixir of Life and Absolute Wisdom [Big Grin]
 

VeeDubb

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Originally posted by Bluestream: The only way to really tell if motor oil is responsible for an increase in fuel economy is to do a test under controlled conditions. You would need to use the same batch of fuel, the air should be the same temperature and humidity level, the exact same route would have to be taken, and the throttle position would also have to be controlled and be consistent. A double blind study would also be helpful. Anything less is really not a scientific study and not really accurate.
You are right. I certainly am not claiming scientific rigor; just anecdotal interest. I also don't buy that synthetics or certain brands are more "slippery" and cause increases in mpg. However, I do believe that thinning or shearing can improve mpg (manufacturers rec. thinner oils all the time to meet CAFE requirements). That is my big concern: did this oil already shear on me? I highly doubt it based on UOA's I've seen, but what else can explain the bump in mpg? I'll have to get it analyzed to know for sure.
 
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I also don't buy that synthetics or certain brands are more "slippery" and cause increases in mpg.
FWIW, my mileage increased by 15% when I switched from dino (5W-30 Pennzoil) to synthetic (5W-30 M1 SS), and that figure has held constant for over a year now. Moving from one synthetic to another, one would think, should show negligable results in mileage. But, stranger things have happened. I'm putting the GC in next week... I'll keep an eye on it.
 
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I have seen a similar effect with havoline synthetic 10w30. vis = 10.1 at 100. If its shearing it hasn't hurt my engine. previously used gtx dino. I gained about 1.5 (very unscientific measurement)
 
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