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6.4 Hemi vs 6.7 Cummins 2021: Horsepower/Durability/Towing Capacity/Fuel Efficiency/Mileage

Are you having concerns about the best engine type between the 6.4 Hemi vs 6.7 Cummins?

Or you presently use one of the two engine types but still consider switching to the other?

If you answered yes to any of those questions, then this article is for you. We have put together this 6.4 Hemi vs 6.7 Cummins guide to help you with all you need to know about the different engine types.

Keep reading to learn more, and remember to drop your comments or questions.

Features of 6.4 Hemi engine

  • 4L displacement
  • Gasoline Powered
  • Hemispherical Shaped Combustion Chambers
  • 370HP for 2019 Ram 2500
  • 429 lb-ft Torque for 2019 Ram 2500
  • 16,320 lbs Towing Capacity for 2019 Ram 2500 pickup
  • Recommended minimum of 89 octane gasoline
  • Oil-to-water oil cooler

Features of 6.7 Cummins engine

  • 7L displacement
  • Diesel Powered
  • 370HP for 2019 Ram 2500 pickup
  • 850 lb-ft
  • 19,780 lbs Towing Capacity for 2019 Ram 2500 pickup
  • 1060 lbs Net Engine’s Weight
  • 66RFE 6-speed automatic transmission
  • Bosch HPCR Fuel System

Differences Between 6.4 Hemi vs 6.7 Cummins

Depending on certain factors, you can decide to go for either the 6.4 Hemi or the 6.7 Cummins engine.

The table below summarizes the major differences to consider. You can also check out this comparison to clarify the differences discussed in the table below.

6.4 Hemi 6.7 Cummins
Horsepower Usually has a higher horsepower compared to the 6.7 Cummins for specific vehicle’s type. For example, horsepower on a 2019 Ram 2500 was found to be 410 hp. It’s preferred for use by owners who are after faster engine and speed. They offer lower horsepower (370 hp) than the 6.4 Hemi for the same 2019 Ram 2500 model. Suitable for use on heavy-duty trucks because it provides higher torque. Hence, they are best used in trucks that would be used to pull loads frequently.
Cost They are generally more expensive because of the high manufacturing costs Less expensive than the 6.4 Hemi engines
Durability They are very durable and are expected to cover up to 250000 miles. However, their durability is improved if you avoid towing heavy loads frequently. More durable and has a maximum mileage of 350000 miles. Their durability makes them the best for towing trucks.
Towing Capacity The maximum towing capacity was 16,320 lbs for the 2019 Ram 2500. However, towing a heavy load upwards along an inclined road for a long time would drastically limit the engine’s speed to about 35mph to avoid revving. They have an impressive towing capacity of 19780 lbs on a 2019 Ram 2500. They also support an auto-level rear air suspension that helps adapt to changing loads or positions. You should consider going for a Cummins engine if you would be towing more often.
Torque Produces a standard torque value of 429 lb-ft when tested on the 2019 Ram 2500. They are always known to produce higher torque values when compared to the 6.4 Hemi for the same vehicle models. For example, a standard 6.7 Cummins engine had an 850 lb-ft torque when used on a 2019 Ram 2500.
­Payload Capacity They offer a maximum payload capacity of 4050 lbs for 2019 Ram 2500. This is possible because of its unique high-speed automatic transmission. When used on the same 2019 Ram 2500, the payload capacity was slightly lower. The value was 3260 lbs. However, the torque rating was higher and boosted the towing capability of this engine as well.
Maintenance Basic maintenance involves cleaning oil filters or having a spare air filter. Besides, only the recommended oil is to be used. They require more maintenance, such as maintenance of emission systems, EGR coolers, head gaskets, and so on. Air filter replacement is also necessary.
Fuel Efficiency Significantly minimized gas consumption through the aid of its Multi-Displacement System (MDS) engineering. It achieves that by shutting down up to 4 out of its 8 cylinders when power is not needed. Turning off the fuel for the cylinders also helps to limit pumping losses of fuel. Offers better fuel management and has a higher miles per gallon (MPG) of 17.5 to the 15.7 MPG for 6.4 Hemi when tested on the Dodge Ram 2500
Mileage With good use and maintenance, the total mileage can be up to 250000miles and above. However, the gas mileage tends to drop significantly during heavy towing. It can go thousands of miles up to about 350000 miles for Ram trucks. However, regular maintenance must be carried out on the engine from time to time.

6.4 Hemi Engines

6.4 Hemi

Pros

Easier to Obtain Gasoline: it is almost certain that you will get gasoline whenever you pass by a gas station or fuel station, whereas getting a diesel station is not as common as gas stations.

Cheaper Fuel: diesel for the Cummins engine are relatively more expensive when compared to gas for the Hemi engines. So, when it comes to daily maintenance costs, the Hemi engines are better.

Fuel Consumption: the 6.4 hemispherical engines now use a multi-displacement system (MDS) that primarily aids cylinder deactivation.

The phenomena involve the engine having to shut down excess cylinders to conserve the fuel consumed instantaneously.

Improved Torque and Horsepower: the intake manifold for the cylinder heads is now manufactured to be vehicle specific.

At low RPMs, the intake valve closes to ensure a low-end torque and opens at higher RPM values to generate increased horsepower.

Large Valve Size: The valves’ side-by-side valve arrangement on opposite sides of the engine means the valves can be larger. The significance of these larger valves is to allow for higher airflow through the engine.

Cons

Combustion Heat Losses: since it’s a large combustion engine, heat loss is higher than it would have been in smaller engines of high-performance vehicles.

High Manufacturing Costs: the cost of production is more than that of many models. Howbeit, the quality it provides commensurate with this.

6.7 Cummins Engine

6.7 Cummins Engine

Pros

Higher Towing Capacity: although both Hemi and Cummins engines can be used for towing purposes, the Cummins is preferred for frequent towing needs because of its higher towing capacity.

Better Fuel Management: minimally consumes fuel because of its excellent fuel to energy ratio.

That explains why the Cummins engine has a higher miles per gallon ratio compared to the Hemi engines. The fuel is also cleaner via the engine’s filters and redactors.

Turbocharger: at low RPMs, fixing the geometry turbo is difficult in some Cummins engines. However, the 6.7 Cummins make use of a very responsive engine that has a slight turbo lag.

Cons

Prone to Head Gasket Failure: compared to the earlier Cummins engine models, the 6.7 Cummins have a higher chance of head gasket failure. Possible causes are high power and torque produced or higher cylinder pressures.

Possible EGR Cooler Issues: with high mileage, there is a high possibility of experiencing emission issues.

One way to avoid this is by practicing proper maintenance. Deleting the EGR system can help too, but might attract legal problems.

Fuel Dilution Issues: although fuel dilution seems to occur in many diesel engines, it might sometimes be more in 6.7 Cummins.

Rather than using the 7th injector to pass fuel into the exhaust, the Cummins fuel injector sprays the fuel into the exhaust stream instead.

So, some of the fuel sticks to the cylinder wall and mixes with the oil.

FAQ’s of Cummins vs Hemi

 How do I get better fuel mileage in my 6.4 Hemi vs 6.7 Cummins?

Increasing your gas/fuel mileage isn’t that easy. However, we have summarized the procedures for you. The first step is to change the oil at specific intervals regularly.

Also, remember to change your spark plugs to avoid burning more fuel than usual. The next step is to warm the engine almost every day.

It’s more effective to take it out for a short ride than warming on the spot. Besides, always check your tires for sufficient air pressure and avoid very fast accelerations. It burns the fuel faster and reduces fuel mileage.

Also, try to check the air filters for clogging. Replace the filters with a diesel performance type if the need arises. Replacing old exhaust systems can also improve gas mileage.

6.4 Hemi vs 6.7 Cummins: Which is suitable for towing in 2019 Ram 2500?

With a powerful Hemi V8 engine, the 6.4 Hemi is very good for towing heavy-duty materials such as construction equipment or building materials.

However, the 6.4 Hemi produces lower gas mileage when pulling loads up a steep surface.

The 6.7 Cummins engine, on the other hand, can tow heavy-duty objects and usually produce higher torque while having maximum towing capacity when installed on the same truck models.

How can I verify that the MDS is working?

Firstly, one wrong assumption is that the ECO light indicates if the MDS is on. The ECO light merely shows that you are driving in a fuel-efficient way which does not necessarily infer that MDS is on.

The truth is that there is no display light designed to indicate the on/off state of MDS. For us, the best way to determine if the multi-displacement system is on or not is to pay attention to the engine sound.

For really loud motor engines, you can quickly tell the difference when the cylinders drop to four.

Is the 6.4 Hemi a small or big block engine?

The modern Hemi from manufacturers is more of the small block definition. Besides, tagging an engine as a small block or big block is not about factory displacement, as some people assume.

The terminology started in the early 1960s to define the smaller dimensioned and lighter blocks as small blocks.

The general view was that the bigger-sized ones, which were heavier, were big blocks for the heavy-duty trucks. They are expected to provide enough torque for heavy use.

Does the MDS feature damage truck engines?

The answer to this question is NO. We understand that there are many concerns considering that only four cylinders operate when the MDS comes on instead of the usual 8.

The main problem is the uneven wear that is likely to happen since some cylinders are hot because they are working while the others are just running cold.

Introducing ACES IV into the fuel would reduce the possibility of this bore wear and other related stems, guide, and valve wear.

However, the manufacturers are aware of this and have modified the valve seats, so MDS issues are unlikely to happen.

The only reason not to use MDS is that you do not feel like doing so. It won’t affect your engine.

Are 6.7 Cummins the best diesel engines?

When it comes to Cummins engines, the reputation for being durable and rugged is hard to ignore.

That is probably because the engine models’ initial manufacture purpose was to be used in heavy-duty trucks. Hence, it has been designed to withstand harsh handling and heavy use.

Today, Cummins engines are now also used in the general automotive industry, and the toughness and durability are still attributed to them.

So, if you are looking for an engine that promises increased horsepower and torque with a good compression ratio, bore, and stroke, the 6.7 Cummins is a recommended choice for you.

What are the possible issues that 6.7 Cummins has?

Most of the issues you might likely encounter with your 6.7 Cummins are usually from the emission parts. The turbos and head gasket can cause problems as well.

Besides, clogging in the diesel particulate filter (DPF) can also occur in Ram 6.7 Cummins. Another possible issue is fuel dilution as a result of the mode of fuel injection into the engine.

However, this does not mean that every 6.7 Cummins engine you buy would experience issues with these engine parts.

It only implies that they are the potential issues your Cummins engine would encounter if any problem arises.

Final Thoughts

Having researched and made related comparisons between the 6.4 Hemi vs 6.7 Cummins, we can see that the 6.7 Cummins engine was the better choice in terms of the maximum towing capacity, the torque produced, and the expected mileage.

They also exhibited a higher mile per gallon ratio for fuel efficiency over the 6.4 Hemi.

Notwithstanding, the 6.4 Hemi engines were found to produce higher horsepower and maximum payload capacity.

Like the 6.7 Cummins, they are durable, although they require lesser maintenance.

So, while it might seem like the 6.7 Cummins are better overall, picking one of the two engine alternatives should be purely based on the proposed application and usage.