Lower MPG after synthetic switch

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I have a 3.0 duratec ford escape with cd4e transmission. 165,000 miles. I switched back and forth between amsoil synethic and walmart supertech conventional and noticed getting <span style="font-weight: bold">fewer</span> miles to the tank with the synthetic oil. What the heck!? any reasoning for this? I get about 30 miles less to the tank with the amsoil vs. the cheapo walmart oil. same weight, 5w20. same route driving too. i don't use a/c.
 
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BrandonVA

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well i prefer to run amsoil but i don't make much money so and couldn't afford it on one of my oil changes.
 
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Originally Posted By: BrandonVA
well i prefer to run amsoil but i don't make much money so and couldn't afford it on one of my oil changes.
That being said, I think I would change my preference to ST all the time.
 
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How many miles between changes? If 5k or less stick with supertech. If I were you I'd stick with a cheaper synthetic, such as QSUD.
 
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Originally Posted By: Brybo86
If I were you I'd stick with a cheaper synthetic, such as QSUD.
Agreed. Also buy a small bottle of Marvel Mystery oil and pour that into the fuel tank.
 
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I don't think its the oil. Perhaps driving habits. I had an 01 escape, i tested 0w20, 5w20, 0w30, 5w30, and 5w 40 rotella. I could not tell any fuel mileage difference in any of these oils. If there is no fuel economy difference in a 0w20 and 5w 40, then there will be no difference in conventional vs syn. Btw the engine was the quietest on mobil 0w30, and thats what i ran in it to 170k miles when i traded.
 
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Originally Posted By: Brybo86
How many miles between changes? If 5k or less stick with supertech. If I were you I'd stick with a cheaper synthetic, such as QSUD.
I noticed a slight decrease in mpg on one vehicle I switched to Amsoil, for the first OCI then it increased after that. ??? But I have also done a UOA for ST Synthetic, and it held up very well at a 5k interval.
 
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Lol oil effecting gas mileage enough for you to calculate during an oil change! Bad gas, driving conditions, variations on how much gas was "pumped in" during your last few gas fill ups, you would need quiet a few data points on the different oils with EXACT same driving conditions in order to even compare let alone come to the "oil is causing it" conclusion.
 
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Its more then likely simply a margian of error. Wind, weather, how much gas is in the tank call all effect your mileage. If you want to talk about wild variables I get many 400 mile tanks and ever so often I get 500 mile tanks. Go figure.
 
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Plus there's also a difference between winter gas and summer gas. I think summer gas has a little more btu per gallon than winter gas. Plus if you don't use a/c, rolling down the windows gives you worse gas mileage than using a/c on the highways. Too many variables. It's really hard to pin something like this on just the oil. Did you also adjust for standard temperature and pressure?
 
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Originally Posted By: Wolf359
Plus if you don't use a/c, rolling down the windows gives you worse gas mileage than using a/c on the highways.
Very true as wind resistance will play a bigger role.
Originally Posted By: Wolf359
Too many variables. It's really hard to pin something like this on just the oil. Did you also adjust for standard temperature and pressure?
I highly doubt it, otherwise we would have some data and calculations to look at.
 
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Originally Posted By: BrandonVA
well i prefer to run amsoil but i don't make much money so and couldn't afford it on one of my oil changes.
Ok, I understand that. Like others have said, try to find an inexpensive name brand synthetic (if you like running synthetic). WM has at least one synthetic on sale every month or so. Right now M1 and PP are $22.66 for a 5 quart jug.
 
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Like Wolf said it may be Winter Formulation gasoline. Another factor is air temperature. On hot days your engine breaths less air because the air is less dense, on cold days more, and the engine has to run at stoichiometric to get good emissions, so that means less gas on hot days than cold. (It also means more power on cold days, once warmed-up anyway). The difference is small, but noticable enough that the hypermilers can quantify it.
 
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