454 Mileage

[dr_goodwrench66]

Just curious what the best tuner out there is for my 454. I cannot do better than 10.5MPG. Engine is in top mechanical shape and has Gibson Cat back, Volant CAI, 3.73 gears, Lucas injectors from Five0...I have EFI Live that I have been working with, but my tuner normally does the diesel stuff. It appears there are lots of good things about ? Thanks in advance!!

 

[454cid]

Just curious what the best tuner out there is for my 454. I cannot do better than 10.5MPG. Engine is in top mechanical shape and has Gibson Cat back, Volant CAI, 3.73 gears, Lucas injectors from Five0...I have EFI Live that I have been working with, but my tuner normally does the diesel stuff. It appears there are lots of good things about ? Thanks in advance!!

How many miles, what tires, and 4wd or 2wd? Is that highway, or in town?

I used to get 12.6mpg on the highway, and sometimes a bit better. 11mpg in town. That was when my truck was new. Now, I think I'm getting 9 or 10 in town, and I'm not driving the highway regularly anymore. I have 240+K miles. I have 4:10 gear, so I would think you'd be doing a bit better.

 

[dr_goodwrench66]

175k miles, 285/75/16 tires and 4wd. This is hwy. In town is 8-9. Truck has fresh intake gaskets, new plugs, wires, fuel filter, fuel pump, distributor, cap, rotor. All GM OEM parts. CMP retard set at +2 degress. Running Mobil 1 5w30 synthetic in engine. I have tried 2 different EFI tunes as well as the latest stock cals from GM Via TIS and I can't seem to gain much more than .5 MPG at most. I have read people on here getting 15 in a 3/4 burb! I was really hoping for low teens...some pipe dream I guess.

 

[454cid]

Well, if the PCM still thinks you're running stock tires, you're actually getting a bit higher......... but you're also pushing more through the air.

Don't forget you're burning winter gas, too........ and how much ethanol is in your gas?

I also wonder if the 285s are too much for the 3.73 gear. When I has 285's I could definitely tell the difference. I was never sure if it was too much tire for the gear, or if it was just shift points. I'm guessing shift points, since sometimes it would shift oddly, since it stopped when I went back to a smaller tire.

 

[michael hurd]

A set of poorly inflated tires as well as an alignment issue could deduct a few percent in mileage for sure. Tires themselves can make a difference, one of my brothers tried 285/75/16 BFG's on stock wheels on his 2005 2500HD, he lost almost 2mpg compared to the stock tires. He was under the impression that his 6.0L was turning too high an RPM for good mileage.

The only difference was the tires. He ended up selling them and going back to the stock 245's.

 

[Vortec Lover]

I was unaware that you 454 guys even knew what the word "mileage" was!

 

[454cid]

He was under the impression that his 6.0L was turning too high an RPM for good mileage.

It's the opposite. Tall tires, means lower rpm for a given speed.

 

[454cid]

I was unaware that you 454 guys even knew what the word "mileage" was!

Of course we do.......we calculate it to the tenth!

 

[michael hurd]

It's the opposite. Tall tires, means lower rpm for a given speed.

He changed from stock sized 245's to 285/75/16 BFGarbage tires since he though that turning the engine slower would net better fuel economy.... Sure the engine turned lower RPM for the same speed... but the mileage dropped by 2mpg.

Install the stock tires, back came the 2mpg lost.

 

[great white]

It's the opposite. Tall tires, means lower rpm for a given speed.

too many variables involved to make that kind of blanket statement if thinking lower rpm = mpg improvement.

But yes, larger rolling diameter = lower engine rpm.