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  #1  
Old 05-02-2008, 01:40 PM
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Bad Gas Causing Bad mileage, or is it Something Else?

1995 E320
206K Miles

This past weekend I filled about half my tank (8 gallons) with gas from a Getty station in Delaware, since it was the only one available before getting on the interstate. I normally use only Sunoco 93/94 or Exxon 93. (The Getty was 92.)

Since then, my fuel economy appears to have dropped noticeably, perhaps as much as 30%. Could this be the result of bad or watered-down gas?

The only other thing I did to the car that weekend was replace my neutral safety switch, during which time the car was jacked up pretty high at the driver-side front, and also during which time I occasionally pushed against a fairly thick rubber hose (vacuum??) adjacent to the transmission and the neutral safety switch. The neutral switch also needs to be correctly realigned, but I don’t think its misalignment should impact fuel economy.

In addition, I have noticed that my oil pressure, rpm and fuel gauges seem “weaker,” sitting at lower than normal levels when the car idles, and my engine sounds quieter than normal.

My first thought was “bad gas causing weak engine performance” and my second thought was “electrical fault in instrument cluster tricking me into thinking my fuel consumption is greater than it is.”

I plan to let the tank run empty before refueling, to burn off as much of the existing fuel as I can. Anyone who has experienced this, please share our thoughts.

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2008 E350 4matic / Black/Anthracite

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Gone but not Forgotten:
2001 E430 4matic, 206,xxx miles, Black/Charcoal
1995 E320, 252,xxx miles, Black/Grey
1989 260E, 223,00 miles, Black/Black
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  #2  
Old 05-02-2008, 01:53 PM
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You need to fill up, drive some reasonable distance, then fill up again. Then you will know what MPG you are really getting. Gauges can have problems as you know.
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1998 C230 330,000 miles (currently dead of second failed EIS, yours will fail too, turning you into the dealer's personal human cash machine)
1988 F150 144,000 miles (leaks all the colors of the rainbow)
Previous stars: 1981 Brava 210,000 miles, 1978 128 150,000 miles, 1977 B200 Van 175,000 miles, 1972 Vega (great, if rusty, car), 1972 Celica, 1986.5 Supra
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  #3  
Old 05-04-2008, 01:22 AM
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Thanks for the reply.

I think it may be partly a quirky fuel guage issue. I was a hair away from empty/R and added 8 gallons -- and the gauge indicated a bit less than 3/4 full.

But mainly, I realized I am way, WAY overdue for new spark plugs and I will address that first.
__________________
2008 E350 4matic / Black/Anthracite

------------------------------------
Gone but not Forgotten:
2001 E430 4matic, 206,xxx miles, Black/Charcoal
1995 E320, 252,xxx miles, Black/Grey
1989 260E, 223,00 miles, Black/Black
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  #4  
Old 05-04-2008, 09:29 AM
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Quote:
Originally Posted by EricSilver View Post
Thanks for the reply.
But mainly, I realized I am way, WAY overdue for new spark plugs and I will address that first.

Not sure if I need to do that yet(?)

My last spark plug change was approx 40,000 miles ago (Jan. 2006), which included a new engine wiring harness, new spark plug wire set, and new OVP relay.

Isn't the spark plug change interval 100,000 miles or 5 years, whichever comes first?
__________________
2008 E350 4matic / Black/Anthracite

------------------------------------
Gone but not Forgotten:
2001 E430 4matic, 206,xxx miles, Black/Charcoal
1995 E320, 252,xxx miles, Black/Grey
1989 260E, 223,00 miles, Black/Black
Reply With Quote
  #5  
Old 05-04-2008, 09:57 AM
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No, spark plugs are every 30k miles.
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  #6  
Old 05-04-2008, 02:55 PM
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Quote:
Originally Posted by deanyel View Post
No, spark plugs are every 30k miles.
Thanks. Plugs have now moved (back) to priority one.

Since all ignition wires were recently replaced, I assume the boots are still ok?
__________________
2008 E350 4matic / Black/Anthracite

------------------------------------
Gone but not Forgotten:
2001 E430 4matic, 206,xxx miles, Black/Charcoal
1995 E320, 252,xxx miles, Black/Grey
1989 260E, 223,00 miles, Black/Black
Reply With Quote
  #7  
Old 05-04-2008, 05:10 PM
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Boots should be part of a new wire set and should still be OK.
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  #8  
Old 05-13-2008, 06:01 PM
EricSilver's Avatar
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Join Date: Mar 2000
Location: Fairfax, VA
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Normality is restored, and mileage may even be slightly better than before.

Odd thing is, the return to normal fuel consumption did not happen immediately, but rather over the course of two or three days.

__________________
2008 E350 4matic / Black/Anthracite

------------------------------------
Gone but not Forgotten:
2001 E430 4matic, 206,xxx miles, Black/Charcoal
1995 E320, 252,xxx miles, Black/Grey
1989 260E, 223,00 miles, Black/Black
Reply With Quote
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