My first concern is what do others get towing with the Cummins?
My gooseneck cattle trailer is about 6,500 lbs empty. I generally get about 12-13 mpg(hand calculated) pulling it.
Second I've heard there is emissions Maintenance on the newer diesels..? What exactly do they have that requires maintenance I know there's def but I don't know how that works?
As far as emissions maintenance, the DPF filter should be cleaned at 200k per Cummins. I would also recommend cleaning the EGR valvle at about 150K which is fairly easy to do. The DPF cleaning is about $300. I am not too sure what the cost of the EGR cleaning is, but unlike the DPF cleaning it does not require any specialized equipment and can be done yourself.
DEF is injected into the SCR(Selective Catalyst Reduction) and turns the NOx(which turns to acid in your lungs) the engine produces into harmless nitrogen and water vapor. Gasoline engines use a three way catalyst that does not require an additive to reduce NOx, but diesels cannot use a three way catalyst due to how lean they burn. You will need to refill the 5.5 gallon DEF tank every 4,000-6,000 miles depending on how you use your truck.
From my understanding a diesel uses a lot lower rpm but does that make it better?
For towing and longevity, yes. Peak pulling power/torque at lower rpm's makes it more usable at normal speeds in every gear when towing. For most gasoline engines that get their peak torque at higher rpm, you essentially cannot reach those peak numbers after second or third gear because you would have to be traveling too fast to reach the required speed to be at the rpm that the engine reaches peak torque. For example, take a 4wd Ram 2500 5.7L Hemi and a 4wd Ram 2500 6.7L Cummins and see what speeds they need to be at to utilize their peak numbers.
Ram 2500 5.7L Hemi 66RFE w/4.10 gears - 400 lb-ft @ 4,000 rpm (not 2500-3500 that was stated earlier)
1st gear: 30 mph
2nd gear: 53 mph
3rd gear: 69 mph
4th gear: 97 mph
5th gear: 119 mph
6th gear: 155 mph
Ram 2500 6.7L Cummins 68RFE w/3.42 gears - / 800 lb-ft @ 1,600 rpm
1st gear: 14 mph
2nd gear: 25 mph
3rd gear: 33 mph
4th gear: 47 mph
5th gear: 57 mph
6th gear: 74 mph
As you can see, after third gear, you would have to be traveling too fast in order to utilize the high rpm peak torque of the 5.7L. In contrast, you can travel at normal speeds to utilize the low rpm torque or "pulling power" of the 6.7L Cummins. Couple that with the fact that the Cummins has double the amount of torque at that lower rpm too.
The other thing about low rpm power is engine wear. As with all moving parts, the faster an engine spins(rpm) the quicker it wears. An engine that stayed at lower rpm for most of it's life will in theory not wear as quickly as one that spends most of its life at higher rpm if all else is the same.
Or is it equivalent to a hemi in terms of how hard it is working to pull..??
No, the Cummins will not be working nearly as hard as your Hemi to make the same pull up hill. It will do it at much lower rpm. The thing about the turbo spinning and working hard is a bit off since the turbo wheels spin at different rates all the time(even at idle) and boost pressure is what is being controlled by the ECM depending on engine load. Another thing about turbos and turbocharged engines is that they are less effected by the thin air of higher altitudes like in Colorado where you travel. A naturally aspirated engine looses about 3% of its power for every 1,000 ft above elevation while a turbocharged engine looses about about 1.5% every 1,000 ft or even less than that with modern turbos.
The common misconception that most people have when they think about diesels is that they apply gasoline engine air/fuel ratio physics to diesels when they are completely different. A gasoline engine has to stay within a certain air/fuel ratio or it will damage the engine. If a turbo was adding more air, then then engine would have to add more fuel to compensate. This is why the ECM on a gasoline engine will add more fuel if it detects more or denser air in order to keep the engine from running too lean. Basically, the amount of air dictates the amount of fuel used. This is why gasoline engines have throttles.
This is not the case for diesels and is somewhat opposite which is why they don't have throttles. Diesels mostly run at an air/fuel mixture that you would consider lean in a gasoline engine. To add more power to a diesel, you just add more fuel and the engine will suck in as much air as it can(with the help of turbos) to burn the added fuel. Basically (without over complicating things too much), the amount of fuel dictates the amount of air used. So instead of the turbo's air burning lots of fuel like a gasoline engine, it would be the fuel utilizing more of the turbo's incoming air which is pushing more exhaust through the turbo creating more boost in a diesel. This is why intakes and exhaust systems not only have larger power gains in a diesel, but also makes them more efficient since there is more air available to help burn the fuel that is added.
How many miles are the Cummins trucks last?
Cummins High Mileage Club
Third what weight of oil is required and what's the cost of oil change if you do it yourself vs a dealer..?? Is it as easy to do it yourself on a Cummins as it is a hemi?
I usually have the dealer change mine every 15k miles since they usually have a special of $65 instead of $75. I don't think changing the oil myself is that much different in terms of ease compared to other vehicles I have owned, but I only did it one time myself so far and the rest with the dealer.
