Over the last few months, I have all sudden lost roughly 2 mpg. I'm thinking maybe a injector, but no oil rising, rough idle, loss of power or white/blue smoke at start up or normal cruising. I do get a puff of black smoke at the initial cold start up of the day (more so w/ cold mornings). I had average hand calculated 16/17 mpg mix driving and freeway 18/19 mpg. I do run Stanadyne every once in awhile and using different fuel stations. To see if that made a difference.

Truck acts the same as always. Could it be anything else besides a injector that would cause loss of mpg? I have no programmers/tuners on my truck, just air flow upgrades. I know the only way to know for sure is run some tests, but want to get a general idea out here.

 

Switch to winter fuel by the local stations perhaps? Not sure what your climate is like, or where in CA you are located, so they may not change the fuel. I've always lost about 2 MPG here when they switch over to winter fuel, but the trucks don't seem to run any different.

 

It started in August when I made a round trip from NorCal to SoCal, I noticed poor fuel mileage. So I started to check every tank since. Running additives and filling up at different fuel stations to see if it made a difference, in which it has not.

 

They wouldn't have switched in August. Sounds like you can rule out the possibility of it being a fuel change.

 

Okay I'm not trying to be mean or make you fill dumb, do you have a CAI? If you do when was the last time you cleaned it? I have friends who said they drop 1-2 mpg when their CAI filter is dirty.

 

What is a CAI?

 

CAI---Cold Air Intake

 

Yes, I do the basic maintenace changes/cleanings as usually w/ my truck.

 

My truck went from 18 around town to 17, which i figured was the new tires so no big deal. It has a slight "vibration" at idle, you can feel it more then you can here it, almost like one or two injectors arnt runnin full blast. This last tank i only got 13.5. No rising oil or white smoke either. When i get on it, the smoke does to have a slightly grayer tint to it, but i thought if it was an injector it would smoke at idle? Dont mean to thread jack, but are problems seem very similar.

 

I experienced a sudden drop in fuel mileage a few months ago. I had just replaced my fuel filters (stock canister and 2-micron) and cleaned my air filter around a week before the mileage drop.

I went on a trip to Albuquerque, filled up my tank while I was there. When I checked my mileage at the next fill up, it was down 2-3 mpg's. Long story short, I changed my filters again, and my mileage went right back up. I must have gotten a bad tank of fuel.

I fueld up at a truck stop, you would think their systems would be cleaner, more traffic through them, more fuel turnover.

It COULD be something as simple as a dirty filter, or in my case 2. I did not notice any different color smoke at idle, nor did I notice any variations or vibrations at idle. I also dumped in some cleaner after changing the filters. I plan on changing the filter again after a couple tankfuls just in case there was still some stuff from that tank of fuel.

CD

 

I do have an AD100 and has been on for the few months since I loss mpg. I hooked it up to my stock fuel canister w/ the 7 micron filter. I figured the stock filter may of had something to do w/ the mpg loss and I took it out. It did free up some restriction by taking it out, but no difference w/ mpg. I would not think the fuel filter on the AD100 is plugged (in two/three months). I never heard of that happening to a FASS or AD system other than using 100% Bio Diesel (sometimes).

So I know my filters are good to go. I will be going to reptable Diesel shop on the 8th of December to relocate my AD100 system to the inside frame and will have them do a injector test to rule it out or the problem.