Well just got back from a round trip vacation to phoenix AZ and then up to lake havasu up the colorado river around lake mead and over to Lake Powell and back through the mountains of colorado and back home.

9 states in 8 days.

Smarty jr on level 3 performance entire trip. followed all speed limits within 3-4 mph most times.

3620 miles total

10 fill ups with schaeffers soy shiel fuel additive every tank.

worst tank was 16.8 don't know why it was so low.

best tank was 20.2.

overall average came in at 19.1 mpg which made me a happy camper.

every tank was hand calculated. temps averaged in the upper 80's to 90's most of the trip with one day at 102.

Fuel prices averaged at around 3 bucks a gallon overall. lowest was New Castle wyo at around 2.50 and highest was around 3.15. Prices vary as much as 40 cents from station to station right next to each other in most states except northern states.

3.73,auto 4x4 short box. quad cab, with access bed cover. Not towing anything but had a lot of camping gear with maybe 500 lbs worth of stuff. That is with a ranch hand bumper and 3 piece stampede bug deflector, mud flaps, factory running boards spray in bed liner. ect just to give an idea of weight.

GPS showed 58.5 mph moving average overall for the trip.

Not bad... I wonder if there was weather (wind etc) that gave bad numbers or bad fuel?

Those were my thoughts as it was windy the first day and poor fuel is always a possibility.

Wow.. great numbers!When I went from ID to AZ this winter (twice, and back).. I averaged 16.46 over the 5046.6 miles, which I still considered pretty good. About 85% of the time the cruise was set at 80. My average speed was 64.54.. I had 2 tanks average over 70, and one over 75. Thou I do have a level kit and fender flares, I don't think either help with mileage. I also had a bed full on both trips, but under the rail. The trips were also with much colder air, which IMHO, makes a big difference on mileage.

I have front leveling spacers also to compensate for the weight of the ranch hand. It sits 1/2 inch higher than stock in the front now. My usual daily driving average with smarty jr on level 2 towing mode is around 16.5 also. but it does better with cooler air 30-70 is the best. I read on numerous threads/forums that smarty jr on level 3 performance yields the best results for milage and this test shows it is accurate info.

I read on numerous threads/forums that smarty jr on level 3 performance yields the best results for milage and this test shows it is accurate info.

From what I can tell that is only on auto trucks... SW doesn't make a difference on manual trucks for cruise mileage.. just timing. I do get the best mileage on TM4, but WOW my oil PLUGS with soot.. don't think I'll run TM4 again.

I have front leveling spacers also to compensate for the weight of the ranch hand. It sits 1/2 inch higher than stock in the front now. My usual daily driving average with smarty jr on level 2 towing mode is around 16.5 also. but it does better with cooler air 30-70 is the best. I read on numerous threads/forums that smarty jr on level 3 performance yields the best results for milage and this test shows it is accurate info.

I am thinking after it goes through the turbo and intercooler, you are seeing 60-90F. Cummins says: Diesel engines are best suited for air temperature s between 60 and 90°F [15 and 32°C]. Engines can withstand temperature s below or above this range, but their efficiency drops. Intake Air That Is Too Hot Engine horsepower fails about 1% for each 10 degrees of intake air temperature rise above 90°F [32°C]. An engine rated at 250 horsepower will develop only 240 horsepower when the intake air temperature is 130°F [54°C] with the same fuel delivery. Air That Is Too Cold Cummins Diesels are rated on the basis of intake air at 85°F [29°C] temperature , but in most localities engines operate part of the time at temperature s of freezing or below. A drop of 60 degrees in intake air temperature results in a 160-degree drop in compression temperature . The knocking of a diesel engine when you first start it in cold weather is a warning that the compression temperature is too low. Low compression temperature s have the following effects on engine operation: Failure to ignite the fuel Delay in ignition of the fuel and, in turn, detonation or fuel knock, and higher peak combustion pressures Irregular combustion and rough-running engine, particularly at idling speeds Possible periodic failure to ignite the fuel charge with resultant dilution, lubrication problems, ring troubles, etc.

ISX has got a point... 3rd Gens moved the IAT sensor to before the turbo... What actually matter is the air temp entering the manifold...

Diesel engines are best suited for air temperature s between 60 and 90°F [15 and 32°C]. Engines can withstand temperature s below or above this range, but their efficiency drops.

Now that he said that the measured air temp on the 2nd gens would be +40*F from the outside air putting it roughly at 100-130*F in the manifold. This is right were I hit my high point in MPG (21-22 MPG)...No wonder my BHAF does so well... Now in the winter time I see temps as low as -20*F and that makes the intake temp about +30*F MPG falls greatly to about 15-16 MPG... So this puts the cold air intakes out the window... But would you believe it this same thing for MPG and IAT relationship also applies to the gasoline Mopar engines too??

ISX has got a point... 3rd Gens moved the IAT sensor to before the turbo... What actually matter is the air temp entering the manifold...

Actually 3rd gens use the sensor in the manifold for Intake Air Temp as far as the injection and calculations are concerned. The sensor before the manifold is mainly used for ambient pressure to compute boost. The temp in that sensor is also used to verify grid heater operation and requirement. My IAT's are about 8-12* above ambient when cruising w/ a/c off, about 10-15* with a/c on. When towing on the flats they are about +15-20*, and when towing hills at 30 psi they are +30-+40. I have seen +45 this year, but the OAT was cooler, the IAT's never seem to get above 130* even when pulling large hills, with large boost, and the a/c on on a 95* day. My IAT's run 5-7* cooler with all the mods I have done, home depot CAI, GDP Intake horn, and Airaid MIT. Until my enigine is at operating temp my IAT's are withing 1* of ambient, unless I hit a stop light, then they go up, but quickly drop to ambient again. Something else I have notcied since my cam install (thou it doesn't mean its from that, just when I noticed it), it that my IAT's jump rapidly when the exhaust brake is applied.. about 10* hotter than they were. This is due to the air flow stopping and sitting in the manifold long enough to get heat soaked.. Turn the EB off and they drop instantly.

Now that he said that the measured air temp on the 2nd gens would be +40*F from the outside air putting it roughly at 100-130*F in the manifold. This is right were I hit my high point in MPG (21-22 MPG)...No wonder my BHAF does so well... Now in the winter time I see temps as low as -20*F and that makes the intake temp about +30*F MPG falls greatly to about 15-16 MPG... So this puts the cold air intakes out the window... But would you believe it this same thing for MPG and IAT relationship also applies to the gasoline Mopar engines too??

Cummins has also put out, in non-specific diesel data, that the IAT should never exceed +30 from the ambient temp. So what data do you believe? I have a different theory on the mpg vs ambient temp... Cold air is more dense, so on a gas engine it does need more fuel to maintain the magic 14:1... But on a diesel the air:fuel is set, so you actually get more power and efficiency with cooler denser air (provided you are running hard enough to keep cylinder temps up). IMHO, what kills mileage in the winter is that cold dense air, and its effect on the frontal area of the vehicle as its traveling thru it. My boost doing 80 doubles from 50* to 0*, it goes from 7-10 to 15-20.. empty cruise. You also have the additional hp required to roll the harder tires, the gear lube is colder, the trans is colder, etc... Those of us that have improved the cooling ability of out trans and diffs are also making them harder to keep at optimal temp when cruising empty in 0* weather. All of those parasitic drains on hp are a much larger impact on a diesel rig that both cold IAT's and winter fuel.. But as we all know its just too easy to blame winter fuel.

Cummins has also put out, in non-specific diesel data, that the IAT should never exceed +30 from the ambient temp. So what data do you believe? I have a different theory on the mpg vs ambient temp... Cold air is more dense, so on a gas engine it does need more fuel to maintain the magic 14:1... But on a diesel the air:fuel is set, so you actually get more power and efficiency with cooler denser air (provided you are running hard enough to keep cylinder temps up). IMHO, what kills mileage in the winter is that cold dense air, and its effect on the frontal area of the vehicle as its traveling thru it. My boost doing 80 doubles from 50* to 0*, it goes from 7-10 to 15-20.. empty cruise. You also have the additional hp required to roll the harder tires, the gear lube is colder, the trans is colder, etc... Those of us that have improved the cooling ability of out trans and diffs are also making them harder to keep at optimal temp when cruising empty in 0* weather. All of those parasitic drains on hp are a much larger impact on a diesel rig that both cold IAT's and winter fuel.. But as we all know its just too easy to blame winter fuel.

I have to agree with you here. I get the same mileage winter or summer. Like when I went to NY at 70-75mph and it was 11F ambient and I got 24mpg. That was nonstop driving. Last time I did nonstop driving I did 70 all the way to denver and only got 21, and it was 70F ambient. There were barely any hills until I got to denver, though it was probably uphill throughout the entire trip. I got the same mileage on the way back though. Cummins does have a point with their 60-90F thing but I do think the "running hard enough to keep cylinder temps up" would offset this. Need more proof but from what I have personally experienced, I think AH64ID is right. As for the frontal area part, I was up to operating temp eventually and never stopped the whole trip so basically showed the true effects that cold air can have on engine efficiency.

I get better mileage the warmer it is outside. Fluids are looser in the truck, the air is less dense and the fuel ignites and burns better in a warmer/hotter engine. I've got 524 miles on this tank of fuel now and the gauge just dropped below 1/4 tank. This'll be a 600 mile tank for sure.

I get better mileage the warmer it is outside. Fluids are looser in the truck, the air is less dense and the fuel ignites and burns better in a warmer/hotter engine. I've got 524 miles on this tank of fuel now and the gauge just dropped below 1/4 tank. This'll be a 600 mile tank for sure.

I filled up this evening..........I had 631 miles on the tank of fuel and filled her with 30.xx gallons of diesel. I don't have the receipt in hand so I'm guessing on the exact gallon amount. Anyhow, I averaged 20.5mpg on that tank of fuel when hand calculated. The overhead "iie-O-meter" read 24.6 when I filled up. I'm happy!!!

I look at it this way as long as you make the 20's club your doing excellent... 16-17 MPG is normal... Below that you better break out the toolbox and find out what's wrong with your truck... These are empty numbers...

I look at it this way as long as you make the 20's club your doing excellent... 16-17 MPG is normal... Below that you better break out the toolbox and find out what's wrong with your truck... These are empty numbers...

On that last tank of fuel that I mentioned, there was also just under 200 miles towing my work trailer around suburbia here. I'm still using 1/2oz per 1 gallon of fuel with my 2 stroke ratio. I've got a real warm blooded truck. The hotter around here the better my truck likes it......mileagewise. I hate the hotter weather......workwise!!!!!! If it never got over 65-70 degrees, this cowboy would be super happy!!!!:thumbup2: