AMSOIL Signature Series 5W-40 Max-Duty Synthetic Diesel OilThe advent of the brand-new API CK-4 diesel engine oil specification has prompted a deluge of new diesel engine oil products from AMSOIL. This is great news for Ram/Jeep EcoDiesel owners as there are now two 5W-40 motor oil options that meet the spec for their engine.

Both of these new synthetic diesel engine oils cover both the FCA/Chrysler MS 10902 and API CK-4 specifications. The API CK-4 spec is backward compatible with the previous API CJ-4 standard. Both of these products will be appropriate for 2014-to-present Ram 1500 pick-ups and Jeep Grand Cherokee models equipped with the 3.0L EcoDiesel engine.

New Elite Synthetic 5W-40 EcoDiesel Motor Oil

The brand new AMSOIL Signature Series 5W-40 Max-Duty Synthetic Diesel Oil replaces the API CJ-4 AMSOIL Premium 5W-40 Synthetic Diesel Engine Oil. Signature Series Synthetic 5W-40 is quite likely the world’s finest engine oil for EcoDiesel engines.

This product ticks all the boxes for discriminating EcoDiesel owners. Here are the highlights.

  • Latest anti-wear chemistry
  • Strong resistance to boil-off in extreme heat and under extended periods of heavy load
  • Capable of ultra-long service intervals.
  • Pours down to -43°C for fast cold-start protection
  • Resists engine deposit formation

AMSOIL Heavy-Duty Synthetic 5W-40 Diesel OilNew Lower Priced EcoDiesel Motor Oil

A new (and quite welcome) addition for 2017 is AMSOIL Heavy-Duty Synthetic 5W-40 Diesel Oil. This economically priced 5W-40 is ideal for fleets or EcoDiesel owners that are minding their maintenance dollars. Here are its highlights.

  • Offers very good wear control
  • Excellent resistance to volatility
  • Has a cold-pour-point of -42°C
  • Resists engine deposits
  • Very attractive price tag

What Is The Difference Between AMSOIL Signature Series 5W-40 Max-Duty and Heavy-Duty 5W-40?

Here are a few main distinctions between AMSOIL Signature Series 5W-40 Max-Duty Synthetic Diesel Oil and AMSOIL Premium 5W-40 Synthetic Diesel Engine Oil.

  • Signature Series 5W-40 offers the ultimate in wear control
  • Heavy-Duty 5W-40 is recommended for OEM drain intervals only, Signature Series 5W-40 has a longer service life
  • Signature Series 5W-40 has a stronger resistance to volatility
  • Heavy-Duty Series 5W-40 has a much lower price

Wear Control

In the Detroit Diesel DD13 Engine Scuffing Test, AMSOIL Signature Series 5W-40 Max-Duty outperformed the test’s minimum standard by a whopping 600%. Heavy-Duty Series 5W-40 achieved a result that was 400% over the minimum standard. Either product will protect your EcoDiesel engine and keep it running like new for many, many years.

Oil Change Interval

Signature Series 5W-40 Max-Duty’s recommended service interval is “Two times the manufacturer’s oil change interval to a maximum of 40,000 km/25,000 miles or one year.” Heavy-Duty Series 5W-40 is to be changed “at the interval prescribed by the vehicle owner’s manual or as indicated by oil life monitoring systems.”

You may not wish to extend the oil change interval beyond Chrysler’s service recommendation for warranty reasons or because of your personal maintenance philosophy. This is perfectly valid. In our personal vehicles, we use the long-drain AMSOIL products because we like the peace of mind knowing that the motor oil is “overbuilt”. While we tend not to push oil change interval limits, we like the fact that our motor oil is offering complete protection for the full interval.


Both engine oils offer exceptional resistance to volatility or oil “boil off” when exposed to extreme heat. In the Caterpillar 1-N oil consumption test, Signature Series 5W-40 beat the test standard by 76%, while Heavy-Duty 5W-40 bested the test standard by 66%.  Either product should handily withstand the heat generated by the EcoDiesel motor.


This is where the choice between AMSOIL Signature Series 5W-40 Max-Duty Synthetic Diesel Oil and AMSOIL Heavy-Duty Synthetic 5W-40 Diesel Oil requires some deliberation. Signature Series wholesales for about 40% more than Heavy-Duty 5W-40. Yet both are great values in relative terms.

Why spend more for Signature Series? Signature Series contains AMSOIL’s best, no-compromise synthetic oil technology. It offers the very latest anti-wear chemistry and is designed for long service life. If you want the very best, then Signature Series is your oil.

There is certainly a compelling case to give AMSOIL Heavy-Duty 5W-40 a long look. It also delivers terrific wear control at very reasonable price.

We’ve Got An EcoDiesel Oil Filter Too

If you’re buying one of our synthetic 5W-40 EcoDiesel motor oils, why not boost engine protection further with an exceptional oil filer? We offer the WIX WL10060 EcoDiesel oil filter. WIX is one of the world’s largest makers of warranty-approved oil filters. We can offer the WL10060 at a vastly better price than the Mopar oil filter offered at your Chrysler dealer. WIX is renowned as a high-quality filter maker. Expect the quality to be as good or better than the stock Mopar filter.

Contact us for a wholesale price list using the form on this page. Put “EcoDiesel” in the “Questions or Comments” section. We have wholesale programs for individuals, commercial businesses and retailers.