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Discussion Starter #1
Hi all, what is the expected MPG for a 1993 Sedan Deville? My car has 114,000 miles and is getting about 14.5 MPG on the highway. I just put new spark plug and wires in it and there was really no change. Thanks.
 

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1993 DeVille
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I have a 93 4.9 with 110k. I got 27 mpg on my recent trip from Fla. to NY.
A lot less around town with the a/c and tunes on.
Showing any codes? Any mods?
 

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Discussion Starter #3
No check engine light or anything; No mods. I will have it checked for any codes; Thanks.
 

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Super Moderator
White Diamond '03 DHS (with DTS floor shift)
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86,781 Posts
You can pull the codes yourself via the onboard diagnostics.
14.5 highway is very low. Like sonjaab said, you should be in the high 20's.
 

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93 SDV, 06 DTS, 2010 STS, 18 CT6
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Definitely a problem. My 93 with the 4.9 does way better. Good YouTube videos detailing code readings.
 

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1993 sedan deville
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My 93 Sedan Deville with 4.9 gets 23 avg according to the digital display. For a lead foot in NH. not to bad. Small town small cities and rural hilly driving.
 

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Master of the Dark Art of Diagnostics
2003 DHS - two-2002 DHS, 2003 SLS, 1995 Sedan DeVille, 1989 Coupe DeVille
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19,254 Posts
my 1995 Deville with the 4.9 ALWAYS got 28.3 mpg on the 400 mile trip between Minneapolis and Chicago -
PREMIUM fuel - AC on - cruise set at 74mph - speed limit then was 65 -
 

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Discussion Starter #9
Wow; yes definitely going on with mine; I drove Houston to New Orleans (~350 miles) and back last month and I got 14.5 MPG tops; That is with new plugs, wires and checking the timing; It's been this way for a while; I will pull the codes and try cleaning the throttle body. Thanks.
 

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Master of the Dark Art of Diagnostics
2003 DHS - two-2002 DHS, 2003 SLS, 1995 Sedan DeVille, 1989 Coupe DeVille
Joined
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19,254 Posts
Wow; yes definitely going on with mine; I drove Houston to New Orleans (~350 miles) and back last month and I got 14.5 MPG tops; That is with new plugs, wires and checking the timing; It's been this way for a while; I will pull the codes and try cleaning the throttle body. Thanks.
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my bet would be failing fuel injectors -
if they are the originals -
the up-dated BOSCH - 4-hole injectors WILL make a difference -

$100 - for a matched set of re-manufactured BOSCH injectors on ebay -
 
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