poor mpg

My MPG has been steadily getting worse. Any ideas on what to check? Upsoluted, no other mods, MAF is fine, power is good, power service or Rotella DFA (lately) at each fillup.

Thanks.

Fuel source varies - this tank I am on Amoco 50, but usually it's 40 cetane.

I just had a Shine suspension installed, so perhaps the alignment is off. And I confess, I haven't checked my tire pressures in a while. I'll take a look at the tires, I don't think the alignment can be that far off.

How many miles on your car?

I have 77K. I have kept track of the fuel usage since new, and have about 130 tanks of data. I made a plot of the data, did curve fits and the like. the peak was at about 10K miles, and was an average of something like 48 mpg in that age. It has steadily fallen, but did a strong dive over the last 10K miles, to about 43mpg. I blame the soot buildup in the EGR. Take off the hose going into the EGR (black hose, 2.5 inch diameter, near the back of the engine. Has a large spring clamp. Slide the clamp back. Pull the hose and look in. I was at least 50% blocked. And as a result, power was not as strong about 3000rpm. I is a pain and a mess to clean, but the power seems better now, and well, I can only imagine the mpg will improve. I will post results in a few weeks.

Dan,
last year at this time, my mileage dropped. Some say it's the winter diesel fuel that is sold and I also think that since our cars take longer (than the average gasser) to get to operating temperature, this too affects fuel efficiency. This will be my second year of tracking through a winter and I expect the same drop off in mileage.

Then, in the spring, it goes back up.

Lito

My mileage has also dropped from about 1100KM-1200KM / tank down to about 800KM-900KM/tank. I always use Sunoco Diesel (apparently it is the best in Canada ). However, they started getting their winterized diesel about a month ago, and that's when my mileage started to drop. My car has 82000KM on it, mostly freeway, avg spd of 120KM/h. So I guess it's still pretty good, I can't complain.

Are you able to access fuel from the same source at every fill-up?? My prior two tanks were Amoco Premier #2 diesel and I got over 800 miles from each tank but I was forced to fill up at the BP Friday and I can tell already that I will only get about 710 to 720 miles from this tank. I use 8 oz. of Power Service each time plus the vent trick. Also, how's your wheel alignment and tire pressure??