Up until October 2012, I averaged 18.75 mpg. Daily driver, 85 miles a day. 70% is highway and 30% is city.
In October it dropped to about 14 mpg and now it is about 12 mpg. The only changes around that time were that I went from 15/40 to 5/40 oil and added a TS Performance 6 pos chip. Other than that, same truck and driving habits I've always had.....
Tried putting the chip to the "stock" position and it does nothing for the better. (was typically running on the 85HP setting.) I haven't tried going back to the 15/40 oil but can't imagine that will increase the mpg back up to where it was.
Looking for suggestions on what may be happening? I live in MN so they started blending the fuel in early December (after the mpg dropped). Fuel pressure at idle was about 45psi (at the schrader) last check.
Truck seems to runs normal, just crappy mpg. Thanks.
Winter fuel could have been formulated in October when you first saw the decline. My truck usually gets 660 to 680 miles from both tanks in the summer and only gets 525 to 540 max with winter fuel using both tanks
__________________
97 F-350-4X4-AUTO 355 GEARS--292,000+ MILES--ROSEWOOD STAGE 1 INJECTORS--SD HPOP--IDM MOD--BTS TRANS WITH SCHAEFER'S OIL --HYDROBOOST BRAKE SETUP-DPP DOWNPIPE--TS 6 POSITION CHIP--TYMAR INTAKE & HX MOD--HAYDON TRANS COOLER--FS 2500 BYPASS OIL FILTER--AMSOIL 5-30 OIL---EVANS COOLANT-203 STAT--WINDSTAR ELECTRIC FAN--DTRL--SYLVANIA SUPERSTAR BULBS- -ROYAL PURPLE SYNTHETIC IN BOTH REARS--WARN LOCKING HUBS--ISSPRO GAUGES IN AUTOMETER 3 GAUGE POD--XL CRUISE MOD--EXPLORER OVERHEAD CONSOLE-AC MOD--BILSTEIN SHOCKS--DB HT STARTER--WESTERN PLOW--CARGORAILS--NRA LIFE MEMBER--LIFE MEMBER SAFARI CLUB
1999 HARLEY DAVIDSON ROAD KING
1992 CONVERTABLE VETTE
2003 E-CLASS 4MATIC WAGON
67 RS/SS CAMARO
97 BMW 528I
Back when my PSD was my daly driver, from 120 to 150 miles per day I got around the same MPG's as you, 18-1/2 to 19+ MPG, even got 20 to 20-1/2 MPG average one summer over 10,000 miles of driving. In winter with 10W-30 oil, a winter-front, and using the block heater every morning I'd still get 17-18 MPG, so blended fuel costs you 5-10% on your MPG.
Like others have said, make sure you dont have a brake dragging, feel your drums & rotors after 30-40 miles of highway non-stop driving. You probably won't like it but I bet your chip has a lot to do with the drop in MPG's. It takes more fuel to make more HP no matter how you do it.
__________________
Denny
'96 F-250 Reg. Cab 4X4 5-sp POWERSTROKE
298,500 mi & NO Problems, LUK Clutch
I see you switched the chip back to stock, but I would try completely removing it and see what happens.
Go back to what you know worked and see if you get results. Then work forward from there.
Yep! I was looking around on the forums for possible resolutions to the MPG issue I am having. There was some talk about pulling fuses to reset some of the electronics. After reading that, It got me thinking and I remembered that when I put my chip in the last time, I forgot to disconnect the batteries... Disconnected and reconnected the batteries on Friday and low and behold... the MPG is back up where it should be!!
The AutoGuide.com network consists of the largest network of enthusiast-owned enthusiast-operated automotive communities.
AutoGuide.com provides the latest car reviews, auto show coverage, new car prices, and automotive news. The AutoGuide network operates more than 100 automotive forums where our users consult peers for shopping information and advice, and share opinions as a community.
Disconnected and reconnected the batteries on Friday and low and behold... the MPG is back up where it should be!! 
Linear Mode
