Tomsrig Posted March 7, 2007 Report Share Posted March 7, 2007 Hi, all, I have a 2000 DeVille wiht 113,000 miles on it. In town I used to get 17 to 19 mpg. On the hwy I got an honest 26 to 28mpg consistently. In August of last year it abruptly stopped getting such good milage. In town I went down to 13 to 14 mpg, and on the hwy 23mpg max. I have always put in regular unleaded, and still do. I change the oil every 3k miles, as some of you said I should do, even though some experts say I should be doing it every 6k miles or so. What's happening with my MGP, any ideas? Tom Link to comment Share on other sites More sharing options...
JimD Posted March 7, 2007 Report Share Posted March 7, 2007 Any trouble codes (DTCs) stored? Jim Drive your car. Use your cell phone. CHOOSE ONE ! Link to comment Share on other sites More sharing options...
Tomsrig Posted March 7, 2007 Author Report Share Posted March 7, 2007 No trouble codes now. But I did start getting a torque converter clutch stuck off indicator, but that was several months after I saw my milage drop off. I reset the TCC indication twice now. It has not come back in a weak of driving at this time. The previous time it took 3 months of driving before it came back on. Could the TCC be causing low milage? I watch the RPM and it still seems the same when cruising at 65 or 70 mph. Link to comment Share on other sites More sharing options...
KHE Posted March 7, 2007 Report Share Posted March 7, 2007 Fuel pressure regulator? Kevin '93 Fleetwood Brougham '05 Deville '04 Deville 2013 Silverado Z71 Link to comment Share on other sites More sharing options...
Tomsrig Posted March 8, 2007 Author Report Share Posted March 8, 2007 I did not change it, but I'll have it checked. No codes that show any problem with it, though. Someone told me that there was a big ethenol change about August of last year that could contribute to the lower milage, They suggested I take it in to the dealer and get a full tune up and spark plug change, and wire change. $350 was the price I was quoted to do all of this. Link to comment Share on other sites More sharing options...
JimD Posted March 8, 2007 Report Share Posted March 8, 2007 Three fifty is pricey for plugs and labor; plugs are $5.00 to $6.00 each. There are no wires. Also there are no DTCs for the fuel pressure regulator. Jim Drive your car. Use your cell phone. CHOOSE ONE ! Link to comment Share on other sites More sharing options...
BodybyFisher Posted March 8, 2007 Report Share Posted March 8, 2007 No trouble codes now. But I did start getting a torque converter clutch stuck off indicator, but that was several months after I saw my milage drop off. I reset the TCC indication twice now. It has not come back in a weak of driving at this time. The previous time it took 3 months of driving before it came back on. Could the TCC be causing low milage? I watch the RPM and it still seems the same when cruising at 65 or 70 mph. While the TCC 'stuck' code is CURRENT, it will hurt fuel efficiency, but I am not sure how much.. If you look at the Poor Fuel Economy chart I posted in this thread, TCC is the last issue... http://caddyinfo.ipbhost.com/index.php?sho...=12914&st=0 Pre-1995 - DTC codes OBD1 >> 1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/ Cadillac History & Specifications Year by Year http://www.motorera.com/cadillac/index.htm Link to comment Share on other sites More sharing options...
Tomsrig Posted March 8, 2007 Author Report Share Posted March 8, 2007 No trouble codes now. But I did start getting a torque converter clutch stuck off indicator, but that was several months after I saw my milage drop off. I reset the TCC indication twice now. It has not come back in a weak of driving at this time. The previous time it took 3 months of driving before it came back on. Could the TCC be causing low milage? I watch the RPM and it still seems the same when cruising at 65 or 70 mph. While the TCC 'stuck' code is CURRENT, it will hurt fuel efficiency, but I am not sure how much.. Thanks for the chart. I'll do the TCC test and see what it says. Tom If you look at the Poor Fuel Economy chart I posted in this thread, TCC is the last issue... http://caddyinfo.ipbhost.com/index.php?sho...=12914&st=0 Link to comment Share on other sites More sharing options...
95SevilleSLS Posted March 8, 2007 Report Share Posted March 8, 2007 I just got quoted putting in plugs for $88. I bought my own for $43. I'm going to put them in myself though. It was a fairly easy job on my 95 SLS and now with the coil over plugs, it's even easier. -Dusty- - 02 Seville STS, white diamond - 93 Sixty Special, Tan with vinyl top - 79 Coupe DeVille, Tan with Tan top - 06 GMC Sierra Z71, Black - 92 Silverado C1500, black and grey - 83 Chevy K10 Silverado, Black and Grey Link to comment Share on other sites More sharing options...
Ranger Posted March 9, 2007 Report Share Posted March 9, 2007 Someone told me that there was a big ethenol change about August of last year that could contribute to the lower milage A lack of ethanol would improve mileage, not hurt it. I agree with KHE, check the FPR. Link to comment Share on other sites More sharing options...
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