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  #1 (permalink)  
Old 17 Jun 2010, 07:56 am
jbcrzn's Avatar
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Default MPG Drop

Greetings again, all. Since replacing the OEM air filter with a K and N standard insert, I have been averaging 23-24 MPG with mixed driving (about 80% in town). This is based on fuel calculations, not the computer which reads that I am around 21-22 MPG. Assuming that both calculations are not going to be extremely accurate, I like to keep an eye out to ensure there is nothing dramatically wrong.

So, I took the PT to the dealer two weeks ago for an oil change and happily drove away with no apparent issues or opportunities. I left the PT in the driveway for the next two days, then fueled up and drove it during the week. When I filled it up right after the service appointment, I had registered just a tad over 24 MPG. After the last two weeks of driving, I checked the computer and it read 16 MPG. I did not think much of it until I refueled yesterday and calculated that I had averaged 18 MPG on the last tank of fuel. Initially, I thought that I might have omitted a gallon of fuel at the previous station, however, when topping of yesterday and resetting my trip computer, with 60% interstate driving, I was not able to break 20 MPG and averaged 13.8 MPG in lighter driving conditions with no jack rabbit starts or anything else that I can identify as problematic.

The only factor that has changed since I returned from the dealer is that my wife drove the PT one day across town, racked up no more than 30 miles. While she does have a bit of a lead foot, I have a hard time believing that the transmission adapted that quickly to her driving and that it would cost me that many MPG's. The only reason I am concerned about it is the severe drop in such a little time. I checked the oil and the transmission fluids and each are fine. There does not visually appear to be anything else wrong, so before I even sound like I am accusing the dealership (which it may be a coincidence), does anyone have any ideas as to what it can be.

Thanks!
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Old 17 Jun 2010, 10:38 am
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Default Re: MPG Drop

Quote:
Originally Posted by jbcrzn View Post
so before I even sound like I am accusing the dealership (which it may be a coincidence), does anyone have any ideas as to what it can be.

Thanks!
...and what are you going to accuse the dealership of doing ?
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Old 17 Jun 2010, 10:51 am
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Default Re: MPG Drop

I would not accuse the dealership of doing anything. I just find it strange that fuel economy is fine for two years and drops well below any reading I have had between having it at the dealership and now. I am merely asking for suggestions of what it could be, so I do not jump to a conclusion that the dealership did something incorrect or that I did something incorrect. I just have a hard time believing that any factor would drop my mileage more than thirty percent in two weeks. I cannot conceive of what the dealership would have, but I also cannot understand what would cause it otherwise. That it why I qualified in my first post that my question is intended to not sound as though I am accusatory toward the dealership.
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Old 17 Jun 2010, 11:18 am
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Default Re: MPG Drop

Lots of things can change your mileage, although if your calculations are correct, it's a big drop. Different types of fuel, even the different blends of fuel (summer/winter) that the station uses. A bad 02 sensor, but you should get a code for that. Dirty air filter. Plugs starting to get old (gap widening).
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Old 17 Jun 2010, 11:30 am
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Default Re: MPG Drop

Fuel with an Ethanol blend will greatly reduce your MPG...Here http://www.fuel-testers.com/2_mpg_e10_gas.html
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Old 17 Jun 2010, 01:06 pm
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Default Re: MPG Drop

Crewzin, what is the life expectancy for the plugs? My Cruiser was born around April 2008 and has 21,000 miles. I will check the plugs. I checked the air filter and it had a single blade of grass that was about an 1/8" wide. Other than that, no gunk or any problems (considering the recent Nashville floods, it was very clean).

Ratdaddy, tell me about it - our Xterra was reaching 21 mpg of mixed use with ethanol free Exxon and now we are lucky to get 15 with ethanol infused fuels. There is a Marathon station that is somewhat near us that has ethanol free fuel. We try to hit that for both of the cars, but I do use blends when I have to do so. The ethanol fuel appeared to be give the PT an extra two MPG over local BP and Exxon stations, while Shell stations appear to decrease efficiency by 2 MPG. I cannot explain that one either.

Thanks, guys!
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Old 17 Jun 2010, 02:03 pm
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Default Re: MPG Drop

If your saying that you have the original plugs and plug wires, you couldn't do any better for your performance and mileage than to change both right now.

If you have any experience with turning wrenches, you can save yourself a lot of money by doing it yourself and have the satisfaction of knowing it's done right. It's a little intimidating to take off the upper manifold but take a look at this guide and it will take you step by step through the whole procedure. Your PT doesn't have any of the EGR things mentioned in the guide so it makes it that much easier.

Any decent set of plugs (gaped at .040in) and anything but another set of OEM wires will set you up for another 50,000+ miles without problems.

Spark Plug Guide
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...just CREWZIN along! . . . PT Cruiser Links Moderator
2000 PT. Original Owner, 123,000 miles
MY technical suggestions are given in GOOD FAITH without total guarantee, if in doubt go to a garage.
Cruiser Of The Month (COTM) May, 2015.
Visit My Home Page www.CREWZIN.com
I find it ironic that the colors red, white, and blue stand for freedom until they are flashing behind you.
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  #8 (permalink)  
Old 17 Jun 2010, 02:40 pm
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Default Re: MPG Drop

Thank you, Crewzin!
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Old 17 Jun 2010, 08:22 pm
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Default Re: MPG Drop

I have noticed that when I take my negative cable off my battery my mpg seems to suffer for a while until it seems the PT relearns my driving habits. Did the dealer have the cable off?
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Old 17 Jun 2010, 10:43 pm
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Default Re: MPG Drop

jb, could it be something as simple as this: the dealer didn't put 5w30w oil into your car--but put in something like 30w. That happened to me once, believe it or not. This would have some negative effect on MPG. Also, your wife may be hauling pigs to market for extra cash--but I seriously doubt it.

Seriously, though has the weather warmed up since your MPGs went south, and you're now using your A/C a lot?

I only get 18 MPG on average. Half city/half highway with the A/C used frequently. But in the winter, I get 24 MPG (the A/C is off, and so is the defroster). So that may also have something to do with it. Check your tires. The dealer may have checked them when they were hot--and let out some air (yes, they have been known to do that). So now, they may be underflated.

That's all I got....

Tim
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