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right frame of mind


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I currently have a 2015 1500 hemi. I have about a 60 mile round trip commute for work. It is ...


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Old 01-08-2017, 09:27 PM   #1 (permalink)
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Default right frame of mind
I currently have a 2015 1500 hemi. I have about a 60 mile round trip commute for work. It is all highway, but a lot of stop and go. The hemi is getting about 16 mpg's right now. My main concern is the long commute. I am putting about 30,000 miles a year on the truck. I can't help but think that a 3/4 ton diesel would be better in the long run due to the amount of miles that I will put on the truck. After 5 years, the 1500 will be worthless and the 2500 will just be "broken in". Is my thinking wrong? Is there something else that I am not thinking about? Just wanting to get the thoughts of different owners with the higher miles on their trucks. Thank you


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Old 01-08-2017, 10:12 PM   #2 (permalink)
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Don't let distance be the only factor. Load levels are also a huge consideration. If you are putting unloaded miles on a diesel, you will have some issues as well. A diesel engine needs a load in order to operate efficiently. Unloaded, the truck will not produce enough heat to keep the motor at peak efficiency. If you don't NEED the diesel for towing/hauling, the gas will be much easier on the wallet in maintenance cost and total investment. Typically the diesel will get the same mileage as the gas truck unloaded. It is only when towing where the diesel tends to get better fuel mileage.

But, if you just want a diesel to have a diesel...party on!


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Old 01-09-2017, 01:09 AM   #3 (permalink)
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Can someone explain why a diesel engine will have issues when used in an unloaded condition. I have hard time understanding why it would be an issue. Isn't the weight of the truck itself considered a "load" already. Many vehicles in other countries use diesel as the main source of fuel for cars and trucks.
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Old 01-09-2017, 04:38 PM   #4 (permalink)
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Originally Posted by MyTruck View Post
Can someone explain why a diesel engine will have issues when used in an unloaded condition. I have hard time understanding why it would be an issue. Isn't the weight of the truck itself considered a "load" already. Many vehicles in other countries use diesel as the main source of fuel for cars and trucks.

Sure not a problem.

What the vehicle is used for is how automakers size an engine (duh right). A diesel engine in a car is only required to carry the load of 4 passengers and some luggage. The difference between empty and fully loaded is a relatively narrow range. Maybe 500-600 pounds. Compare that to a heavy duty truck and the range is much wider. From 7K pounds empty to 25-30K fully loaded. The engine has to be built to handle the super heavy loads so the cooling systems are sized according to the high end of the tow rating.

Because the cooling systems are so efficient (and huge) on the heavy duty trucks, when unloaded, the cylinders never get hot enough to burn off all fuel. This causes fuel to contaminate the oil, removes oil film from cylinder walls, adds soot to the turbo and injector tips, and can cause issues with the emissions systems on modern trucks. Newer trucks have design features to help mitigate some of these issues but a diesel truck is most efficient when loaded.

This is also why you are seeing very small (relative) diesel motors in the new half ton trucks. They don't need to be as heavily loaded to work efficiently.

Hope that clears it up.


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Old 01-09-2017, 05:20 PM   #5 (permalink)
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If the coolant temp gauge reaches operating temp which is about 185-190 deg, this tells me the engine is at working temp range. Loaded or unloaded, the engine is working at the designed range in terms of temperature. If the truck is loaded, the coolant temp would rise but settle back down. So if the coolant temp gauge is used as a measurement of efficiency, then I don't see how loaded and unloaded conditions would affect the decision whether to buy diesel or gas.

I think the term efficiency can be taken in another way. By using diesel, the MPG does not really change too much as compared to gas when driving loaded or unloaded. For gas motors, MPG is dependent too much on the load and its rpm.

I bought my Cummins based on the uncertainty on whether I will have an
RV trailer or not. I didn't want the truck to be the limiting factor on what size RV I can buy. The people I work with who have RVs all told me to get an HD diesel truck. Nothing less. Some tried the 1500 and some tried 2500 with gas but they all said diesel is the way to go. Towing a RV trailer is a difference of 1500 rpm for diesel versus 4000 RPM for gas. I think the only penalty in buying the diesel is the maintenance. 3 gallon of DELO+$15 oil filter+2 fuel water separator gets expensive. The air filter is expensive too. The DEF fluid is not too bad.

I have a RV travel trailer (6000 lbs). When the wife packs up the whole house, it is about 7000 lbs. I realized after a year with the RV travel trailer, I need a bigger one such as a fifth wheeler with slideouts. If I had bought a 1500, it would be a problem.

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Old 01-10-2017, 04:08 PM   #6 (permalink)
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Originally Posted by MyTruck View Post
If the coolant temp gauge reaches operating temp which is about 185-190 deg, this tells me the engine is at working temp range. Loaded or unloaded, the engine is working at the designed range in terms of temperature. If the truck is loaded, the coolant temp would rise but settle back down. So if the coolant temp gauge is used as a measurement of efficiency, then I don't see how loaded and unloaded conditions would affect the decision whether to buy diesel or gas.
Cylinder temperatures and water temperatures are very different. You can have stable water temps but have the EGTs vary greatly. It is the high cylinder temperature produced by heavy loading that burns off the soot on the injectors and turbo and helps burn the fuel more completely. Efficiency for the sake of my argument basically getting the most energy from the fuel. This can only be done if all the fuel is burned in the cylinder.

It's not going to kill an engine in 50K miles if you never put a huge trailer on the truck but it is just something to keep in mind if you want to go 200-300K miles and have a healthy engine/injectors.


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Old 01-10-2017, 04:29 PM   #7 (permalink)
 
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I thought people only bought diesel trucks to lift and put -44 26" wheels on...

Originally Posted by Diller View Post
Because the cooling systems are so efficient (and huge) on the heavy duty trucks, when unloaded, the cylinders never get hot enough to burn off all fuel. This causes fuel to contaminate the oil, removes oil film from cylinder walls, adds soot to the turbo and injector tips, and can cause issues with the emissions systems on modern trucks. Newer trucks have design features to help mitigate some of these issues but a diesel truck is most efficient when loaded.
Never had a problem with having a diesel and not towing, but what you're saying makes sense. The short trips are what kill diesels (unless you always have a load). We have turbo's go out on the rig trucks we have - some the FE's fault and others are just bad design. Ford put the DPF system on and it will only clean out when you're rolling. When we pull up to rig we might idle for 5 minutes or 5 hours so we don't have the option to go drive down the road. The FE's tell me that they had a couple 6.7 Ram's and they couldn't keep them out of the shop so that's why we run Ford only.
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Old 01-10-2017, 05:32 PM   #8 (permalink)
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Originally Posted by Diller View Post
Cylinder temperatures and water temperatures are very different. You can have stable water temps but have the EGTs vary greatly. It is the high cylinder temperature produced by heavy loading that burns off the soot on the injectors and turbo and helps burn the fuel more completely. Efficiency for the sake of my argument basically getting the most energy from the fuel. This can only be done if all the fuel is burned in the cylinder.
I forgot about the EGT. Now I understand.

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