We all know the last of the 5.9's was the most powerful, and least fuel efficient of the 5.9's.

 

Cummins didn't put an external EGR on the truck to help it along, but to meet emissions they had to keep cylinder pressure lower by retarding timing... less power, higher EGT's, etc..

 

The common consensus is that a peak cylinder pressure at 9-12° ATDC is best for performance, and efficiency. That means that all the fuel needs to be injected, and ignited prior to that point so the pressure hits when it should.

 

Take a look at this chart and you might see why the EGT's are high and fuel efficiency is lower. This is how many degrees ATDC the injector stays open. Top is rpm's, and left is MM3. OEM tuning runs up to 132mm3.

Still on the same tank of fuel from my above post.  Just thought I'd add this picture for y'all.  Took it whist driving today to go dog train.  Shows the level left in my fuel tank and how many miles I have (at the time) on the tank!!  Enjoy................I sure am!!      

It seems that even CR engines are affected by the warmer air.

Warmer air is two fold, but mainly the resistance is lower and the fluids are always warm. 

 

It goes back to winter temps kill winter mileage, not winter fuel. Many people refuse to believe it, but it's true.

 

It simply takes less hp to drive at speed in summer than winter, the a/c does hurt but not as much as the warm air gains.

 

My car mileage usually peaks in April, warm enough to be very efficient and minimal warm-up and not using the a/c often. Once it get really hot I lose about 1 mpg over April, but still 1-2 better than winter.

 

I might look into the files and see if I can find out much timing is even changed by IAT on a CR.

My low fuel light just came on driving home from work today.  Here's a picture for y'all.

Warmer air is two fold, but mainly the resistance is lower and the fluids are always warm. 

 

It goes back to winter temps kill winter mileage, not winter fuel. Many people refuse to believe it, but it's true.

 

It simply takes less hp to drive at speed in summer than winter, the a/c does hurt but not as much as the warm air gains.

 

My car mileage usually peaks in April, warm enough to be very efficient and minimal warm-up and not using the a/c often. Once it get really hot I lose about 1 mpg over April, but still 1-2 better than winter.

 

I might look into the files and see if I can find out much timing is even changed by IAT on a CR.

 

The one trip of mine back from NoDak that I've referenced a few times here was in temps of about 20*F.  Twas roughly the same temp at home as when we left.  We did have a 10-15mph NW wind blowing us home;  but I was running the truck 75-80mph, and still got right at 21mpg.  Just the truck loaded to the gills with 3 guys, 2 dogs, and hunting gear for 4 days.  Just saying.

My best tank was also in cold weather, sub freezing for most of it. The kicker was the 1000' drop over 300 miles and the 10-15mph tail wind.

 

I didn't say you can't get good mileage in cold, you just get better in warm air under identical conditions otherwise.

 

 

I didn't say you can't get good mileage in cold, you just get better in warm air under identical conditions otherwise.

 

 

I agree 100%!!!

Filled up today just as the DTE on the Lie-O-Meter hit 0.  Wound up with 720 miles on the tank and filled up with 32.4 gallons for an average of 22.2mpg.  Probably about 80-90 miles of the tank were towing my work trailer.

546.xx as the needle centers the 1/4tank mark.  Could be another 700+mile tank............but I've gotta work tomorrow and the  next day towing the trailer.  Overhead Lie-O-Meter is reading 27.8mpg and  246DTE.

My current tank, only 1/3 burnt, is looking very good. I was about 220 miles at 3/4, normally I am ±110 towing and ±180 empty. I ended up towing the TT 18 miles, and now am hooked up to the TT with a full load, around 19K GCW, so the mileage will drop quick on my way to fuel up... but I would say I was all of 20-21 for the first 200 miles of the tank, very good for me.

546.xx as the needle centers the 1/4tank mark.  Could be another 700+mile tank............but I've gotta work tomorrow and the  next day towing the trailer.  Overhead Lie-O-Meter is reading 27.8mpg and  246DTE.

 

 

This tank wound up at  21.3mpg.  Not complaining one bit.

 

The tank I'm on now will be a typical summer tank and be in the 19-20 range.  Much more towing.

 

Have a Kentucky trip scheduled for Sunday-Wednesday.  I'll post mileage results.  Plan on going down with the 3 dogs and some carpentry tools to help a bud frame out an "out-building" on his property.  I'll keep the speeds at my normal 65-68mph on the Interstate to and fro.

This tank wound up at  21.3mpg.  Not complaining one bit.

 

The tank I'm on now will be a typical summer tank and be in the 19-20 range.  Much more towing.

 

Have a Kentucky trip scheduled for Sunday-Wednesday.  I'll post mileage results.  Plan on going down with the 3 dogs and some carpentry tools to help a bud frame out an "out-building" on his property.  I'll keep the speeds at my normal 65-68mph on the Interstate to and fro.

 

Kentucky trip report...................

 

Left my house with 2.5 miles on the tank of fuel as I fueled up about 6 hours earlier.  Drove down to Berea, KY;  spent 2.5 days there and drove back to the NW side of Indianapolis, IN all on 1 tank of fuel.  That's 724 miles, and I stuffed 32.7 gallons in;  for an average of 22.1 mpg.  Was running 65mph with 10mph crosswind to and fro.

Twas another 215 miles home after the fill up. 

 

Truck ran great.  Just under 210,000 miles now.

Edited July 10, 201410 yr by dorkweed

It seems that even CR engines are affected by the warmer air.

My 05 does way better mileage in hot weather and or in the mountains. Normally hangs in the 16 mpg range easy dd around here, last trip a few years ago to Phoenix and back 4500 miles in 10 days averaged 19.8 overall lots of hot weather and mountain driving that trip.

I truly believe now that the "free-spin" hub kit has gained me at least 1mpg.............................and that's saying after 40,000+ miles after the install!!!  I think I can say that for me being more anal than most about mileage and such. The hubs run cool even in really hot weather......................they ran warm just after the install but I think that was just the bearings "setting/breaking in" IMHO!!

 

If I hadn't done the free-spin kit;  it'd be a matter of a few more months where I'd be changing the front axle U-joints based on historical averages for my truck.  Just rotated tires and lubed the front end, and the axle U-joints look great. Pumped int the grease and got grease oozing out from all the cups on both sides.

 

I make it a point to lock the hubs about once per month and drive about 30-40 miles to make sure the U-joints and the front diff seals stay lubed.

I'll chime in here with my '06. drive 75 miles one way to work running 72-85mph lie-o-meter says 28+to 27.4. Actual measured is 19-21 depending on where I fueled. If I keep the speed below 70, I gets up to 35+ on the lie-o-meter. Never had the chance to measure that, for actual milage.