How To Get Better Mileage From An Automatic?

My company just stuck me in a new automatic Peterbilt 579 and I'm averaging about 5.9 mpg. When I was driving a manual 579 I was getting about 6.8 mpg. What gives? I thought autos were supposed to be better on fuel consumption.

My company just stuck me in a new automatic Peterbilt 579 and I'm averaging about 5.9 mpg. When I was driving a manual 579 I was getting about 6.8 mpg. What gives? I thought autos were supposed to be better on fuel consumption.

Mine is a Freightliner, so might be geared different. I get 7-9mpg.

I find that often the automatic will go all the way down to first at a stop. I manually shift to second or third depending on the load.

Also, is yours skip shifting when you take off like you did with your manual? If not that might be using extra fuel going through gears it doesn't need to.

Is yours a true automatic or what they call an automated manual transmission (amt)? Mine is the amt. you might wanna ask your maintenance people if there are any programming parameters missing. On mine they had to reprogram when I first got it.

Also, I find that I have to slow down a little on take offs. I used to go slower because I was shifting, but the automatic just takes off when I put my foot down and sometimes that's not letting the transmission work efficiently.

I hope this helps.

I had an automatic Pete for a bit and it averaged about 8mpg. I don't know why yours is getting such low mileage.

If you normally cruise the interstate at 60-65mph, and the tach is around 1300, that's the mileage you get.

Shifting up and down on a normal trip is a microscopic amount of your total miles.