Lost 6 mpg.

[Spartus]

Just turned 30k today, and She's worn out. :confused: Better MPG is city than highway?

I recently made a long trip with no trailer. It was 356 miles round trip, 95% highway, and cruised at about 75mph. I only managed 16mpg. I always cruise at 75-80mph even when towing ever since I got the truck new, so the speed is not a factor here.

The same trip last year netted 22mpg.

I also towed 6,000 lbs last year and got 16 mpg.

This last winter (5k ago)I had two injectors replaced because they were leaking. I also only have about 5k on the current fuel filter and oil change.

So, bad injectors still? I made another 200 mile trip earlier this winter after the injectors were replaced and only got 18mpg instead of my normal 22mpg. It seems my mileage is getting lower and lower the more I drive the dang thing.. Funny thing is, around town I still get 16-17mpg.

So, SAME MPG city and highway?????? This is very odd.........

Any ideas appreciated. Thanks.

[ 06-06-2005, 01:04 AM: Message edited by: Spartus ]

[More Power]

How was the truck equipped when it delivered better fuel economy, and how is it equipped now?

Is there a tire size difference? Are you using a power adder that you didn't have before? Install a suspension lift? Etc, etc.


MP

[ 06-06-2005, 12:49 PM: Message edited by: More Power ]

[Spartus]

Thanks for the reply. The only addition is a coating of rhino lining on my nurf bars. Not enough weight there to make any difference. I run Bridgestone 285's on it, and have had those on it since the truck had 1,000 miles on the clock.

The rear axle was also swapped out 2 weeks after the injectors were changed because the dealership screwed up the preload on the pinion nut when changing the pinion seal, and tore up the R&P.

This truck has always had impessive mileage. Now that highway is lower than city I'm rather puzzled.

I checked the oil again today, and with 5,200 miles on it, it's right at the full mark, and still looks fairly clean with NO diesel smell to it.

Oh, also I do have a juice module. It's been on the truck since it had 2,000 miles. Removed only for dealership visits. I run at at level 1 all the time.

[More Power]

The tire size you're using will produce both a real and a calculated reduction in fuel economy. Correcting the speedo/odo will bring some of the calculated mileage back (due to a math error), but larger tires increase rolling resistance somewhat and could reduce fuel economy when compared to the factory tires - though I sure wouldn't expect as large a hit as you reported.

If the fuel economy decline coincides directly with the rear differential work or fuel system replacement, I might think there's a connection.

MP

[cabletech]

When you had your fuel system work did they update the PCM software? I had my truck in for a no start problem & when I got it back my mileage went down. The mileage is even worse towing. I later found out the tech updated my PCM to the latest software. I don't blame him, but I'm mad due to the loss of fuel mileage. If I put my juice on it just makes it worse (towing or not). Sound like the problem you are having?

[Spartus]

MP, as stated above the tires have been on the truck since I had 2,000 miles on the clock. I always multiply by 1.07 when doing my arithmatic too. Less tread on the tires, so I feel that 1.08 is over doing it.

356 miles x 1.07 = 380 miles / 23.8 = 16 mpg. I ran it down to fumes almost, trying to get home.

That mileage plain ole sucks.


CableTech:
Sounds similar to me. Maybe when I take it in to get my broken baljoint boot, and turn signal switch fixed I'll have them "check" what revision I have in there if possible.. In August of 03 I had it flashed with a newer version to fix my 4x4 selector switch issue, but mileage has always been in the 20-22 range until lately.

I dumped in 2 bottles of that DieselKleen today, we'll see what happens on the next tank.

[DmaxMaverick]

Originally posted by Spartus:
I dumped in 2 bottles of that DieselKleen today, we'll see what happens on the next tank. What size where those bottles? 32 oz? I'm sure you didn't use the 96 oz'ers. Even so, 16 oz. per tank (25 gals) is the recommended max. I understand the desire to boost it a bit, but I think that may have been overboard.

I use the Power Service stuff, too, and usually use it at full strength, 16 oz. per tank. I can really tell the difference in power, mileage (pays for itself) and smoothness at +6 cetane, vs. +3, and with no additive. I've tried it at a higher dose (32 oz/tank), and didn't notice any improvement over 16 oz.

[Spartus]

Two gallons.. Is that too much? It seems to break the tires loose with anything over 1/4 throttle now.

Actually,
I used:
Two 8oz bottles.. I usually use 8oz per tank.

I only seem to use it every 4-5 tanks though.

[Kennedy]

Originally posted by Spartus:



I dumped in 2 bottles of that DieselKleen today, we'll see what happens on the next tank. I'd suggest trying something good like FPPF Total Power, Primrose, or Stanadyne Perf Formula additives.