Engine/Transmission (1994 - 1998) Fuel Plate Fuel Mileage & ULSD

[RWorth]

Need your opinion. I have a #10 plate installed and set conservative. AFC adjusted to help keep the smoke to a minimum, and I also have DDP stage 2 injectors installed with stock turbo. The truck has been set up this way for about 7 months. I pull a 5th wheel and goose neck stock trailer. I don't hot rod the truck, I just pull my trailers or drive empty. The truck is a joy to drive except my fuel mileage seems to have really dropped. When running a #11 plate, set agressive, and stock injectors after fill up a half tank would be approx 300 miles driving empty but now if I get between 200 and 250 miles I feel pretty fortunate.
I ran the #10 plate with stock injectors anf fuel milage was about the same.

With fuel prices the way they are I am thinking about having my stock injectors ckecked and re-installing them and going back to a #11 plate.

I guess to me even installing a bigger fueling plate set conservative and AFC adjusted to minimize smoke and driving with a lite foot fuel mileage shouldn't drop the way I am seeing my fuel mileage drop.

 

[fox]

Is the air filter clean? I know a bumb question.

Has the timing slipped?

If you are driving for best mileage, the fuel plate won't even need to in it, as it shouldn't be touched.

Keep the rpm at 1600-1700!

That is what my 95 auto loved. It would get 23 on the highway by keeping the rpm under 1900.

 

[LPittsley]

I have seen a similar drop in mileage too. I have dropped to 16mpg daily driving and 17 to 18 mpg. I used to get 18 back and forth to work. It is hard to chase a few miles per gallon drop. I've basically changed as you have except going to DDP3's. I've got an auto too. So less coming out of the pump. You can read my sig. Good luck. Willy.

 

[GAmes]

I'm thinking winter blend, but it may be your supplier if you buy fuel in the same place all the time. Try a different station. I recently filled my tanks at the Flying J in Waco, Tx. The next fillup was in Wytheville, Va and my mileage was 20. 5 hand calculated. That fuel gave me 18, and I'm sure it was because of the blend.

 

[Vaughn MacKenzie]

Keep the rpm at 1600-1700!
That is what my 95 auto loved. It would get 23 on the highway by keeping the rpm under 1900.

It is interesting how different trucks like different RPM. If I run my mostly- stock '98 auto that low I can't use much throttle without EGTs rising quickly. . . 1600 is only good for loafing along empty on the flat. Gotta get it up to 1800 to pull good. Mine seems happiest & gets its best MPG at 1850-2050 RPM on the highway.

Vaughn

 

[TStrite]

How much are you towing? Thats about the mileage I get grossing 26000, maybe a little better. My truck likes the 1800-2000 rpm range also, go much more and mileage drops off.

 

[RWorth]

Correct me if I am wrong. The fuel plate profile is design for the governor arm to travel once the AFC arm is out of the way so if the profile is deeper than stock this allows for more fuel with more air = more HP. If I drive the truck like I always have then a diiferent plate allows more fuel when you need it. I can see where bigger injectors could possibly effect fuel mileage because of nozzle size allowing more fuel into the cylinder instead of going back to the tank from the return lines. Does my thinking seem right? The 5th wheel is 9900lbs. when completely empty, the stock trailer is a 6'8''X20' gooseneck. When pulling the 5th Wheel I can usually get to 160 to 175 on a half tank. I usually run about 65mph which is about 1850 rpms. I know I am not the only one seeing a drop in fuel mileage and I do know that winter blend causes a drop, but is the ULSD causing big drops in the fuel mileage.

 

[Vaughn MacKenzie]

How much are you towing? Thats about the mileage I get grossing 26000, maybe a little better. My truck likes the 1800-2000 rpm range also, go much more and mileage drops off.

A car on a flatbed or a 20' travel trailer. . . grossing half what you are