Isx15 horrible mpg

First thing is I hope whomever removed those items from your truck put in a good program for the computer or fuel mileage will be the least of your worries.

How many miles on it?

 

Problem is, you bought an ISX! Do a little more research next time.

 

Fix with Volvo D13 XE , throw away ISX

 

I have an ISX15 485hp backed by a 13 speed Ultrashift Plus and 3:55s. I also average 8mpg hauling steel.

I considered doing a delete until I did some serious research into it. That whole motor is a single organism with every part supporting every other part. Deleting the EGR can lead to possible cracked heads due to overheating if the delete isn't done correctly.

Personally, I'm keeping my after treatment system. I'm just looking for more economical methods of cleaning and maintaining the system. The possible associated costs of a delete just do not make financial sense to me.

You want to run without it? Cool and good for you. I'd recommend getting yourself a pre-EGR truck then, and get very familiar with your tools (a good idea no matter what truck you run).

 

I'm at 7.3 lifetime with my ISX coming up on 700K miles.

10 speed manual/ 3.58 rears.

With 3.55's, you're gonna need to slow down.

Once you're cruising over 1400 rpms, it's gonna suck fuel.

 

I had a Volvo with D13 and 3.55's.

It was all I could do to get 6.2 out of it.

 

What's your boost pressure reading? Have you tested your charge air cooler for leaks?

Is fuel doser injector still plummed up? Could be dripping fuel into exhaust.

 

Yours must be set up.different somehow from mine, Dave. Mine gets the best fuel mileage cruising at about 1530 rpm. Puts the motor right up close to the top of the powerband, and let's me walk up the Kentucky hillsides without issue.

Today, for example. 523 miles (big day for me), 60 gallons burned. My math shows that as just a hair under 8.72 mpg. Not bad with 43,000 on the deck coming out of Kentucky to the other side of Erie, PA.

 

You are doing really good on your fuel mileage. Wish I could do as good as you. I would be thrilled to get 8 mpg