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Discussion Starter #1
I am mechanically inclined & have always kept my vehicles in great shape. I am older , so I drive like a Grandpa, & don't have any bad habits that affect mpg. No hills, [ Fl. ] , but A/C on a lot.
My 2003 ZX3, Zetec , 5 spd. , 52,000 miles , always got around 35 mpg [ combined ]. Then came 10% ethanol in gas & it dropped it to 32-33. The last 2 tankfuls I have seen it drop to 26mpg ! It runs pretty good but seems to have lost a little power & I notice a little skip, once in awhile while accelerating. NO codes are showing up at all.
It has 52,000 miles, & at 30,000 a new fuel filter was installed. Also ,new Autolite plugs & wires at 35,000. It has a new air filter, & PCV valve. PCV hose is good . Good quality fuel injector cleaner was added in the last tank as well as throttle body & MAF cleaned . Tire are inflated to 35psi. It idles fine .
This SUDDEN drop has me puzzled & I would like to see a return of better MPG. As I said,, no codes have shown up on OBD code reader.
Any help & tips will be appreciated.
 

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I'd recommend the Motorcraft plug wires, you can get them from www.rockauto.com for under 50.00 shipped, I haven't had good experiences with the autolite wires. Also, on my car I changed the upstream oxygen sensor and coil pack, mileage and performance went up even though the car wasn't showing a CEL before I did this.
 

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Hatch Nation #136
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Take a look at the pigtail running into your ignition coil. They've been known to go and it doesn't always throw a code while it is giving up the ghost.
 

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Discussion Starter #4
Thanks.
I will look at the coil wires, today. I will check into the Ford wires as well. I think I even saved the old wires I took off & I can reinstall to see if there is a difference.
I can always get top mpg out of every car I have owned, but something has happened , now.
 

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Hatch Nation #136
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Also, just a thought...

Have you unplugged your battery for any reason recently?
 

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Could be the fuel itself

Here in the Detroit area, I notice my MPG changes from fill up to fill up. Some gas stations give me great gas miles, others suck .Sometimes I think its just cheap blended gas. Sometimes the gas really smells bad as i pump it. Water, comtaminates, cheap gas blending the consumer always get the shit end of the stick. Just my two cents.
 

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Discussion Starter #7
No I haven't disconnected battery.
I thought about the idea of gas having additional ethanol added to it, lately. It is supposed to happen, I understand. I bought gas at different stations lately, [ BP & Chevron ] & had low mpg with both. Car is in immaculate condition , but I live where 75% of my driving is on lever rural roads @ 55-60mph , & I need to find the sudden , large drop in mpg.
 

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Change the fuel filter again, if you are at 52 now and it was changed at 30 that was probably a few years ago based on that mileage. The last few years I was changing my Zetec fuel filter yearly. I think the 10% ethanol fuel clogs them quicker or maybe you got a batch of dirty gas and the filter did its job or a combo of both. If you DIY its easy and cheap to change fuel filter, the part should be $15 and minimal tools are required.
 

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Discussion Starter #11
UPDATE ;

I had saved the old original wires & put those back on . World of difference ! I ordered a set of new Motorcraft wires & will replace the fuel filter, too. If that doesn't completely solve the problem , I will make another NEW thread .
Thanks for the help, guys !
 

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I have the same sudden drop in mileage. Went from 30.5 average in mixed town highway driving to 29. Worse, the highway mileage went from 45 to 38. (I'm a fairly slow driver)
Could it be transmission reprogram which I had done last fall?
2012 focus with 15,500 miles total.
 

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It could also be "winter gas blend" as many cars see a drop in mileage.
 

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Thats What She Said
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a change from 30.5 to 29 is not a large or even sudden drop. Winter blends impact it but that should have been used sine November time frame for most gas stations. How do you measure your MPG? did you fill up the exact same station same pump? did you let it auto click off and leave it at that or did you fill more in? if you fill up at a different station, and are a a slightly different incline you can put more or less fuel in. the auto turn off will vary with temperature and with pump. You need to trend it over time. I would not trust a MPG change unless it showed constantly lower for more than 3 repeated fill ups at the same station using the same pump.
 

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Do you buy fuel at same place every time? Just because they went to 10% ethanol means nothing. Here in Texas they can put anything around that number, dealers routinely check ethanol percentages in fuel to verify warranty violations so customer complaining has to pay for the work, of course customer has no idea what's in the fuel. Even though the federal mandated max amount is supposed to be 10%, very often it is more, as high as 20 in some cases. They tilt the fuel with more alky to make your mileage drop so you have to buy more fuel and faster. Occasionally it even gets high enough to cause engine problems, Walmart stations went through that a while back. The finger pointing between Walmart and Murphy Oil was pretty funny.

Try different station for fuel, the problem has been covered by newscasts here in the D/FW area. New cars get good mileage, then suddenly they don't........

If they ever allow 15% as legal watch out. The fuel suppliers claim it will not hurt cars, but they already know since they have been doing it in some cases for years. At first they hated ethanol, but they have learned to embrace it and even love it, just one more hard to trace method for ripping off the public.
 

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A drop from 30.5 to 29 is not so great, but a drop from 45 to 38 is. Now, This is my second winter with this car and the mileage problem is new. It could be ethanol but I don't know. I buy fuel at Arco which is a sub of BP.

Who controls the ethanol content of fuel?
 

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What's your 2012 rated to get on the freeway? Lots of factors can do that, say you have unusually windy days and always have a strong head wind. Or your tires have dropped 1/2 a psi due to an extra cold front, or the salt on the roads causing a little more rolling resistance. You did not fill up all the way, or might have had a small % more of ethanol in that tank.

Is ARCO really a sub of BP? I HATE ARCO with a passion and refuse to go to their stations when I am in CA. Its the refinery I believed that does the blend, but I think the stations may have some say on what they order. It should be a MAX % of possible ethanol but I don't think its regulated or can be since it can vary by fuel truck delivery.
 

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Supposed to be 10% but the recent congressional debacle over going up to 15% has some places thinking they can legally go to 15 now. EPA sets it but different in different areas based on pollution readings. Big cities more likely to have it and rural maybe not unless their air swept by city air to pollute it. Here in Texas it was like 7 major counties around Houston and Dallas, recent non-attainment expanded that to many more surrounding counties. The station fuel pumps should have a sticker on side saying they have ethanol in fuel. Refineries control the actual amount but sometimes after the fact blending goes on out in the field.
 

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Had a sudden drop today as well. Track my mileage every tank for a year and it's always been clear what the problem has been - snow, winter tires, ethanol, heavy foot, etc. Have been running Shell V-Power for 3 months or so now, no ethanol, and enjoying it. 27.5 MPG calculated when I filled up this morning, which is good and normal for me driving mostly city, occasional spirited driving. Now down at 3/4 remaining and only 60km on the odometer. Has me a little worried but will go into work early tomorrow morning and hook up the laptop for a quick drive while monitoring real time MPG.
 

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MPG tests showed normal fuel consumption. I think my 'slow fill' problem caused me to not get a full tank of fuel making it appear to be bad mileage..

Had a sudden drop today as well. Track my mileage every tank for a year and it's always been clear what the problem has been - snow, winter tires, ethanol, heavy foot, etc. Have been running Shell V-Power for 3 months or so now, no ethanol, and enjoying it. 27.5 MPG calculated when I filled up this morning, which is good and normal for me driving mostly city, occasional spirited driving. Now down at 3/4 remaining and only 60km on the odometer. Has me a little worried but will go into work early tomorrow morning and hook up the laptop for a quick drive while monitoring real time MPG.
 
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