Workhorse 8.1 liter poor fuel mileage
I have a 2005 Fleetwood Southwind 37c with the 8100 Vortec V8 with an Allison 5 speed transmission with 28000 miles that gets very poor gas mileage, about 6 mpg towing my boat or pickup and 7 mpg empt...
Forum Discussion
I would start with the basics as was mentioned, replace the air filter and fuel filter.
The other thing to check is the MAF sensor. It sits in the intake airflow between the air filter and the intake manifold and measures incoming airflow. The PCM uses that info to determine fuel delivery, and if dirty, could result in the engine running rich, which would explain both the low mileage and the black tailpipe.
The MAF is easy to remove but it is delicate. Be sure to use the aerosol MAF cleaner, NOT carb cleaner, or Brakleen or other chemicals. Take it out, spray it, put it back in after it's dry.
You might also consider plug and wires...even though you only have 28k miles, those parts are 10 years old now, and wires can break down due to heat cycling and cause a weak spark, which could cause incomplete combustion and also blacken the tailpipe.
No codes set because nothing is "broken", only little things that are each taking their toll and adding up to a 1 mpg or so cost.
FYI, I have 160k miles on my 8.1, and averages over the years have been 11-12 on the hiway, 10 around town, and about 7-8 towing. I have found that mileage has improved 1 mpg across the board since I changed to Mobil 1 Hi-Mileage oil last year.
The other thing to check is the MAF sensor. It sits in the intake airflow between the air filter and the intake manifold and measures incoming airflow. The PCM uses that info to determine fuel delivery, and if dirty, could result in the engine running rich, which would explain both the low mileage and the black tailpipe.
The MAF is easy to remove but it is delicate. Be sure to use the aerosol MAF cleaner, NOT carb cleaner, or Brakleen or other chemicals. Take it out, spray it, put it back in after it's dry.
You might also consider plug and wires...even though you only have 28k miles, those parts are 10 years old now, and wires can break down due to heat cycling and cause a weak spark, which could cause incomplete combustion and also blacken the tailpipe.
No codes set because nothing is "broken", only little things that are each taking their toll and adding up to a 1 mpg or so cost.
FYI, I have 160k miles on my 8.1, and averages over the years have been 11-12 on the hiway, 10 around town, and about 7-8 towing. I have found that mileage has improved 1 mpg across the board since I changed to Mobil 1 Hi-Mileage oil last year.
