Strange drop in fuel mileage

[JanAndBill]

I've been running anywhere from 10.5 to 11.0 mpg while towing. Yesterday I came across north Alabama, two lane roads, hills and curves, fuel mileage dropped to 10.5. This morning I fueled at a Citco truck stop in MS because it was the only one I could get into, and came north into TN on 45. The farther I went the more it felt like the truck was pulling harder than it should have been, but the fuel mileage was holding at 10.5. As I crossed the river into Missouri on I55 which is level and flat, my fuel mileage dropped to 10 and seemed like I was pulling all the time??? There was a little head wind but not significantly strong. I've never ran Citco diesel fuel before, has anyone else had this happen???

 

[marvmarcy]

Dirty/watery fuel can do this, but even a 10-15 mph headwind might do it as well (or both). Even 5 mph difference in speed can cause a fuel eonomy change like that. Brand seldom makes much difference, since most local fuel stations get deliveries from the same distributor.

 

[dfk009]

May want to try the Ford PM 22-A cetane booster & performance improver. Have to use it in my 6.0, because fuel in Missouri/Illinois has a low cetane rating. This has straighten a many Ford out that has gotten bad fuel, before I retired from a Ford dealer.

 

[JanAndBill]

Dirty/watery fuel can do this, but even a 10-15 mph headwind might do it as well (or both). Even 5 mph difference in speed can cause a fuel eonomy change like that. Brand seldom makes much difference, since most local fuel stations get deliveries from the same distributor.

The bootheel of Missouri is notorious for wind, so it could have been an issue, but there wasn't much indication of it in the trees and such along the road. I even stopped and checked the truck and trailer to be sure I didn't have a brake dragging. I had this happen once before in GA. One day fuel mileage went down, next day after I filled up, it went back up.

 

[brianharrison]

Are you able to see calculated load on your tuner?; I am not familiar with the SCT. Can you log? You would be able to compare calculated engine load across different scenarios. Brian

 

[VLaurie1799]

Check all the simple stuff, air filter,low pressure in a tire, fuel filter getting close to being full, got a dose of water. I would try a new fuel filter and put a good fuel conditioner in fuel and check all the other stuff. I use hawes fuel conditioner all the time. When truck was new I picked up a mile per gallon empty, more than pays for the conditioner, not to mention what it does for the injectors and pump.

 

[VLaurie1799]

Sorry, you checked for a brake hung up, what about a wheel bearing starting to fail. Try carefully putting your hand on the hubs when you first stop, should be quite warm if one is really hot better get that wheel apart. Also you can jack up one wheel at a time and rotate and wiggle the wheel listen for a grinding noise or when you wiggle there should be no play in the wheel. This is not a replacement for taking the hubs apart once in a while and check the bearings. Hope all this helps you find a problem, this issue can be so many different things.

 

[JohnDar]

The road may appear to be level and flat to the eye, but is it really? Even a slight incline will drop your mileage a tad.

 

[JanAndBill]

The road may appear to be level and flat to the eye, but is it really? Even a slight incline will drop your mileage a tad.

I-55 from AR line to Benton, MO, is Mississippi Delta. It's so flat and nothing but farmland as far as the eye can see.

 

[JanAndBill]

Checked all the simple things, no brakes dragging, hubs ok, serviced air cleaner and filters before I left. Had this happen once before and it cleared up as soon as I refueled. My SCT has the ability to log, but I haven't downloaded the software on my laptop to be able to view it. Might have to.

 

[VLaurie1799]

It could have been a batch of poor fuel, it improved with the next fill.

 

[dbbls59]

I-55 from AR line to Benton, MO, is Mississippi Delta. It's so flat and nothing but farmland as far as the eye can see.

It appears flat but it is upstream.

 

[JanAndBill]

It appears flat but it is upstream.

To get our drivers to be more fuel efficient they received a bonus for fuel mileage. One driver always complained about any run we put him on going north, never a complaint on east, west, or south. I finally asked him one day why he always complained so much about loads going north. His response was because he couldn't get his mileage bonus pulling a load uphill all the way. What????? He then pointed to the large map on my office wall - see he said, "everytime I go north I'm going up!!!" It was easier to just have his dispatcher keep him in the on an east/west lane than to try to explain to him.

 

[Netem]

I think you may have been bucking more wind than you thought. We drove the DWs car south to Cape today and got 33.2 on the way down and 30.1 on the way home. (north)

 

[JanAndBill]

Switched back to street tune yesterday, haven't really driven enough to determine the mpg, but it seems like it's still a little low. Trying to get the tank as low as possilbe before I refill. The BH 3260 has so far seemed to be very areodynamic but I guess the wind could be an issue. I'll know when we head out again with a new tank of fuel.

 

[dewwood]

A little head wind, or for that matter a diagonal or even side wind, can make a fairly significant change in fuel mileage. A change of 1 to 4 MPG is not that unusual. We dropped from a normal of around 11 towing to 6.2 on one trip across the Texas panhandle but it was quite windy. When we stopped at the nice Welcome Center I could hardly get my door open because the wind was blowing so hard. That is an extreme but 2 or 3 MPG is not unusual. Figuring your mileage on a longer trip with all types of driving will give you a much better estimate of how your vehicle is doing.

 

[JanAndBill]

On street tune since Sunday, and local miles I was doing good to get 14.5. Filled up today and within a few miles my mileage started slowly creeping back up. Same in town and local driving but it's back up to 15.5. Still think I got some bad fuel. Going to get some Ford PM -22A additive tomorrow, and try that for awhile.

 

[Tool958]

I had lost mileage on my truck. It had dropped about 2-3 mpg on average and couldn't figure out what was going on with it until it started throwing a reduced power code. The trouble with that was that it was showing no code numbers. Finally decided to clean the MAF sensor with MAF sensor cleaner. It immediately brought the mileage up along with stopping the codes. That lasted for about a week and then the reduced power codes came back. Cleaned the sensor again and really made sure I got in all of the little holes and the bottom of the sensor. I actually blew some black gunk out of it the second time around. So far the mileage has stayed up and no more codes.

 

[JanAndBill]

Thanks Don, I get back next week I'll go ahead and clean it. So far since I refilled, my fuel mileage is coming back up. I'll know for sure tomorrow, have about 200 miles to tow.

 

[brianharrison]

Non chlorinated Brake Cleaner also works well for a MAF cleaner. I have sprayed it into a ziploc bag and soaked the MAF sensor that way, shook it around and blow dry with light compressed air. I make sure i do not touch the sensor - do not use a q-tip or any other direct mechanical cleaning; that can damage the sensor.

Hope this helps,
Brian

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