Why is my mileage so bad? - Diesel Forum

Satans F350 · 01-11-2010, 12:34 AM

I realize the lift & tires kill mileage but I'm currently getting about 10 mpg avg with 50/50 city/hwy. I drive like an old lady but the mileage still sucks. I hear the famous "whooshing" sound every time the tranny shifts. It still makes the sound after warmed up so I'm leaning toward the wastegate as the culprit. I've read some other posts about leaking up pipes, how would I know if that were the case? Also where is the CPS located and what color should it be after the recall? I've only had this truck for 2 months and I'm trying to figure everything out on it.

jacksonbend · 01-11-2010, 02:11 AM

I took out my Superchip and picked up over 1mpg. Picked up 1-3 more depending how much hwy w/my TS.

Satans F350 · 01-11-2010, 10:48 AM

I just got the superchip last week to try to improve mileage. I can feel the power increase but I'll have to wait to see if the mileage improves through a couple tanks. I thought about the TS chips but don't have gauges currently and my wife's not patient with PSD mods so went cheap off ebay with the superchips.

indystroker · 01-11-2010, 02:55 PM

Winter blend fuel is not the best for mpg either...but 10 mpg is still low. Here is an old link about winter fuel. Good info, even if its not the culprit.

TheDieselStop.Com Forums: Can somebody set me straight on winter diesel fuel.

RT · 01-11-2010, 03:55 PM

The CPS is on the front of the motor -looking down over the radiator it will be just to the passenger side of the harmonic balancer. It should be grey after the recall - black is original equipment and blue would only be there if you got a late model CPS. The blue apparently causes a rough idle and diminished fuel economy. The F-350 probably has 4.10 gears, so your not going to get the 19 mpg I get with my F-250, but it shouldn't be 10 either. When it gets warm enough to go outside again (that's April or May in Oregon, right?) Check your EBS sensor tube (check out Guzzle's directions here: Welcome to guzzle's Exhaust Backpressure Sensor Cleaning Maintenance Web Page) - I would also run some Stanadyne through the tank and make sure your fluids are all changed. Outside of the engine - jack up your front wheels and make sure they spin freely - Ford caliper pins can get sticky and your brakes will drag. You'll have to jack up the whole rear end and put it in neutral to check the rear - limited slip, you know.... I've got a lot more ideas, but I'd start there. Don't forget to air up your tires like the president said....