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sudden drop in mpg

 
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Old 10 Sep 2012, 07:12 pm
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Question sudden drop in mpg

my PT Cruiser has been getting 23 mpg in town and between 28 and 32 mpg on the highway. It has suddenly dropped to 20 in town and 26 on the highway. I have been advised by a couple of different sources that this is a result of the EPA changing the ethanol mix to 15% from 10%. Has anyone heard of this, or is it just another story. If it is not that does anyone have any suggestions as to what could be causing the problem. My cruiser is the base model 2008 with a manual transmission. It has 45000 mile on it. I change the oil every 3000 miles and use 10-30 synthetic. I also poured in a bottle of injector cleaner at my last fillup.
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Old 10 Sep 2012, 07:35 pm
mdfrodolives's Avatar
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Default Re: sudden drop in mpg

Well ... my manual says that 5W30W is the preferred oil to put in our PT's--due to energy (gas) conservation.

Also, your mileage is a lot better than I have gotten in California for the past eleven years.

Tim
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Old 11 Sep 2012, 07:55 am
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Default Re: sudden drop in mpg

I agree with frodo. Are you sure you've been calculating it correctly? My 2010 has 27k miles and doesn't even get 23mpg on the highway, so I don't see how you could be getting that in town, unless your town has no traffic or lights.

I realize the manual will be a little better, but not that much better...
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Old 11 Sep 2012, 09:13 am
quicksilverdon's Avatar
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Default Re: sudden drop in mpg

When was last time you replaced plugs and wires? The stock wires are CRAP.
Get a name brand of wires and gap plugs at 0.050.
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nurtured by the false notion that democracy means that 'my ignorance is just as good as your knowledge."
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Old 11 Sep 2012, 09:17 am
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Default Re: sudden drop in mpg

Quote:
Originally Posted by geocacher View Post
my PT Cruiser has been getting 23 mpg in town and between 28 and 32 mpg on the highway. It has suddenly dropped to 20 in town and 26 on the highway. I have been advised by a couple of different sources that this is a result of the EPA changing the ethanol mix to 15% from 10%. Has anyone heard of this, or is it just another story. If it is not that does anyone have any suggestions as to what could be causing the problem. My cruiser is the base model 2008 with a manual transmission. It has 45000 mile on it. I change the oil every 3000 miles and use 10-30 synthetic. I also poured in a bottle of injector cleaner at my last fillup.
the less ethanol, the better the mileage. not vice versa. we use e85 for drag racing as a cheap alternative to racing gas and generally you need to adjust the car to use 30% more fuel.

nice name btw. geocaching is fun. we stumbled onto a box while climbing a bluff at devils lake.

when we got home we went on a few adventures. geocaches are EVERYWHERE! there's an ammo box in the woods by my house we are going to track down next.
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Old 11 Sep 2012, 09:30 am
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Default Re: sudden drop in mpg

well like allt he rest mine has never ever got over 27 ever and mine lives on the interstate at almost 200 miles a day if I ever got 32mpg Id most likely wet all over myself
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Old 11 Sep 2012, 01:02 pm
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Default Re: sudden drop in mpg

Quote:
Originally Posted by geocacher View Post
my PT Cruiser has been getting 23 mpg in town and between 28 and 32 mpg on the highway. It has suddenly dropped to 20 in town and 26 on the highway. I have been advised by a couple of different sources that this is a result of the EPA changing the ethanol mix to 15% from 10%. Has anyone heard of this, or is it just another story.
The stickers displayed on the pumps by me still read "Up To 10% Ethanol". That means 10% or less, say maybe 8/9%. A change in mix from 10% to 15% would maybe mean no more than a half a MPG but most likely nothing notable. You would just be a hair leaner at worst. If your car is slightly rich like most cars to start with, there really is no "worst" that should happen with a possible bit more power. If greater proportions of ethanol are used, then the injectors would need to be retuned for a longer duty cycle or even replaced with bigger injectors. And then, yes, you would see less miles per gallon as a result. Some people say they notice a mileage difference between summer and winter mix but I've never noticed that myself where I live in Texas, so I don't know about that.

Most people don't take the time to do the actual math to figure mileage. I'm talking about the guys who say "I get xxx miles per fill up". That's a lame way to calculate. Take the miles since the last fill up and divide that by the gallons to the second or third decimal point to figure the miles per gallon. Any other way is a trash number. I'm not saying you are doing it wrong because I don't know. I'm just mentioning it for all the Linkers reading this thread, "just in case".

A few other things that impact mileage are dead weight in the car, under inflated tires, running the A/C, bad tune and subtle changes in traffic conditions. A mechanic friend once told me that any amount of unburned fuel that adds up to a drop bigger than a BB per mile will throw a trouble code.
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Old 11 Sep 2012, 01:50 pm
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Default Re: sudden drop in mpg

Quote:
Originally Posted by 2step View Post
Most people don't take the time to do the actual math to figure mileage. I'm talking about the guys who say "I get xxx miles per fill up". That's a lame way to calculate. Take the miles since the last fill up and divide that by the gallons to the second or third decimal point to figure the miles per gallon. Any other way is a trash number. I'm not saying you are doing it wrong because I don't know. I'm just mentioning it for all the Linkers reading this thread, "just in case".
Correct! The most accurate way to calculate mpg is to divide the miles you drove on a tank by the number of gallons you took to refill the tank. Make sure you fill up the same way each time. For example, if you top off to the next dollar, do that each time. If you stop when the pump stops, do that each time. It will take a few fill ups to get a good overall average mpg.
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Old 12 Sep 2012, 05:50 am
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Default Re: sudden drop in mpg

Quote:
Originally Posted by quicksilverdon View Post
When was last time you replaced plugs and wires? The stock wires are CRAP.
Get a name brand of wires and gap plugs at 0.050.
Make that gap 0.040....

Also, about mileage - doing one tankful is meaningless - you need about 1,000 miles (several tanks) to get a realistic measure, due to gas pump shutoff variations.
__________________
"Anti-intellectualism has been a constant thread winding its way through our political and cultural life,
nurtured by the false notion that democracy means that 'my ignorance is just as good as your knowledge."
Isaac Asimov"

'05 Limited Turbo Lite, (Silver, of course)4-wheel ABS, Sunroof, Spoiler. Mods: E&G Classic grill, K&N FIPK, BTG duals, rear lowered 1.5", LED washer lights, $20 catch can, Aoogah horn, Weatherflectors, Sunroof Deflector, Fuzzy Dice, rear logo flames, rear pinstripe graphic, Gen3 Taillights, rear sway bar, hood struts, Strut bar.
Traded in '02 Silver Touring Edition w/87,000 miles
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Old 13 Sep 2012, 01:08 pm
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Default Re: sudden drop in mpg

My PT cruiser is the base model 2.4 liter with a manual transmission. This may explain why my mileage has been better than most. I also have been driving it gently since the price of gas is getting out of hand. I have used 5w 30 weight synthetic at times in the past and have not noticed a measurable change. I check my mileage every tank full, and use the old fashioned division method. I attempt to fill the tank the same each time, but if I didn't I would see an increase or decrease depending on how much more or less I put in each time. Sorry to hear that you are not getting better gas mileage. I live in a small enough town that I don't spend half my time sitting at a light or in a traffic jam which will kill your mileage in a hurry. I am still questioning whether the EPA has changed the amount of ethanol allowed in our gas.
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