8 mpg by driving 55

Easy to do pulling a van with these newer trucks with auto.

 

There's a lot of people on this site that mother #### the MX 13 all day long.

It's a low rpm engine.

Everyone I have spoken to in the real world that has one thinks it's the greatest thing ever.

 

I have a w900 3406e turned up to 750hp with 2250lbs of torque. 13 speed with 3.55 gears. Running an open deck pulling heavy loads around 70 mph in the Midwest I can get 7mpg if I treat that pedal like there's an egg under it. Once I get rolling though I can still hammer it down when need be occasionally with great results.

 

I’ve never gotten much above 7 with my 389. It’s not the most aerodynamic truck in the world and it’s got 600hp. I used to do reefer work last year but now i’m 90% heavy haul so 3 tractors on the back aren’t as aerodynamic as a van with skirts and those doorflap looking things in the back.

 

I did that a few years ago when fuel was 4 bucks a gallon and I was on paper logs. But it is mind numbing and dangerous.
You loose about 10th of mpg with every 1mph over 55, so if you’re getting 7 at 65 you should get 8 at 55, all things equal.

 

That Lucas Oil additive works wonders! Once those fuel injectors get squeaky clean, watch the power and fuel efficiency increase

 

So what do you think a 12.7 Detroit burns at idle? A gallon an hour sounds slim.

I can definitely see the gauge has moved in the morning after 12 hours ideling

 

A mechanic told me setting the cruise at 62-63 mph is a trucks sweet spot. It's also a lot easier on the truck, less wear.

 

I have a 99 classic so I don't have the most up to date stuff. I find running 55-60 I will get 5-5.5mpg. If I increase my speed to 65-70 I'll go up to 6mpg. I have a isx 600 18 speed 3.55 rears. One speed is not right for all set ups. You have to find the right speed for your truck. For best fuel mileage. If I could see 8mpg with my truck I'd be dancing in the street bragging to everyone. I know I could pay a truck payment by getting a newer truck with better mileage. I like the idea of payed off stuff.