Mostly Mechanical

Auto & Truck Oils, Lubes & Filters – Separating Technology from Hype

CJ-4 Diesel Oils only for 2007 & later models – they’re NOT for earlier diesels!

DO NOT use CJ-4 oil in vehicles prior to 2007 models, unless you want increased wear and more frequent oil changes: because the 2006 and earlier models do not have diesel particulate filters (DPF’s), they do not need the restricted formulation of these CJ-4 oils. 

Amsoil’s new DEO oil is a premium 5W-40 synthetic diesel engine oil that is certainly among the best examples of the new CJ-4 emissions-spec oils.   In fact, it’s one of the only examples: most oil companies still don’t have a CJ-4 diesel engine oil formulation, much less have it available in the U.S. market as of October 2006.  Even more kudos to Amsoil, because their CJ-4 oil performance is still better than most CI-4+ oils, and because it’s proven – it has already logged over 12 million fleet miles.

To be fair, this article title isn’t completely true:  if you’re changing your fleet over to Amsoil and take it all to CJ-4 so that you can be certain of always using a DPF-compatible oil, you are still getting a better performing oil across your entire fleet than your current petroleum CI-4+ oil.  So don’t take me wrong.  

But while this CJ-4 oil is the best that Amsoil can formulate within the specification requirements, and it is the best performer available in this group, the CJ-4 spec does compromise oil performance with brand-new limitations on the oil additive contents.   This is why Amsoil only recommends DEO “for use according to the longest service interval established by the engine, vehicle or equipment manufacturer”: there is concern that the additive package cannot handle the dramatically extended (25,000+ mile) drain intervals with the conservative safety margins that Amsoil’s other diesel oils are designed for.   Oil sampling analysis will be a more essential element than ever before in fleet management for 2007+ diesels.  

So in 2006 and earlier model diesels, always use the 15W-40 (AME) or the high-fuel-efficiency 5W-30 (HDD) if your goal is to maximize fuel economy and engine life while minimizing your maintenance costs.  Amsoil will NOT be discontinuing these CI-4+ oils anytime in the foreseeable future.

Which oil should you use for 2006 and earlier diesel models?

The two best choices on the market – per the published technical performance test data, field fleet testing, and product warranty – are the Amsoil 15W-40 Premium Heavy Duty Diesel & Marine oil (product code AME), or the Amsoil Series 3000 5W-30 Heavy Duty Diesel Motor Oil (product HDD).  Despite your owner’s manual recommendation of a 15W-40 oil, your PowerStroke/Duramax/Cummins/Volvo/Caterpillar engine – like nearly all engines – is designed to use a 30-weight oil.  The 15W-40 recommendation is not based on engine design, but on the assumption that 40-weight petroleum oils will often “shear back” to a 30-weight oil in diesels, and if you use a 30-weight oil that shears back to a 20-weight oil you will have wear problems (or worse).  Of course, AMSOIL’s full PAO synthetic HDD formulation will maintain viscosity as long as you are using it as recommended in a healthy engine (no fuel getting in the oil, for example) – so your engine will enjoy year-round benefit from the 30-weight oil it was designed for. 


Both oils are 25,000 mile oils that outperform every other available diesel oil on the market, and are LESS EXPENSIVE to use because of those extended drain intervals.  Both oils are also superb performers in gasoline engines.  Either oil will work well for you, but my best recommendation is for you to make an informed choice based on your specific needs.  Here are some suggestions to help you:


        For this Application…                                         Pick this oil:

             Fuel Economy                                           Series 3000 5W-30 (HDD)

    Cold Temperature Performance                             Series 3000 5W-30 (HDD)

    All-fleet oil for home/farm/garden                          Series 3000 5W-30 (HDD)

            Lowest oil usage                                              15W-40 (AME)

          OTR Freight Hauling                                 5W-30 (HDD) – or 15W-40 (AME)*

       All-fleet oil for class 3-8                              15W-40 (AME) – or 5W-30 (HDD)*

All-purpose oil for logging/heavy-construction                    15W-40 (AME)*


*While it is difficult to compare them, Engineers generally agree the thicker 15W-40 (AME) will provide slightly more wear protection than 5W-30 (HDD) in extremely heavy applications, particularly off-road/gravel/rock-crawling applications where drivetrains are subject to heavy torsional shock-loading.  However, for highway/city mileage, HDD fuel economy savings probably exceed savings from reduced wear with AME – if there is any reduced wear at all with AME in highway/city driving.

More diesel info here


October 23, 2006 - Posted by | Diesels, Lubrication Oils & Fluids, Vehicle Maintenance


  1. This is nothing more than an Amsoil commercial. I seriously doubt that their CJ is any better than any CI+4.
    On the Turodiesel register site, they have documentation showing all CI+4 Oils far superior in additives than any CJ.
    In particular, Ashland oils CI+4 made for Cummins seems to be one of the best ever. NAPA also has a similar Ashland CI+4 variant.

    Comment by Peter Surprenant | November 10, 2007 | Reply

  2. [Corrected & improved some content in this, on 2/17/08] I should have been more specific that the post deals specifically with recommendations for AMSOIL CI-4+ vs. AMSOIL CJ-4+ diesel oils. And the main point is that the CJ-4+ spec forces lower performance maximums than CI-4, due to the restrictions on ZDDP and sulfated ash. Yes, the CJ-4+ oils are “backward compatible” with CI-4+ oils, but they do NOT offer as much protection. For those reasons, the best choice on the market (highest performance and best total-lubrication-cost value) for a 2006 or earlier engine will be AMSOIL’s CI-4+ oils: the 5W-30 Synthetic Heavy Duty Diesel Oil (HDD product code), or the 15W-40 Synthetic Heavy Duty Diesel & Marine Motor Oil (AME product code).

    On TDR, Robert Patton put it this way on 7/15/07:
    “The conclusion is that the new CJ lube oils are a compromise as they do not have the same additive package as the previous CI/CI-4 plus oils.” I certainly agree with that statement, and the 4-ball-wear-scar size and TBN numbers both reflect that: in general terms, CJ-4+ lubes will allow higher wear rates, and must be changed more frequently to avoid acidic oil.

    “Seriously doubting” something doesn’t add information or change test data. I didn’t say AMSOIL’s CJ-4 was better than every CI-4+, but a comparison of standardized test results will show that it IS better in performance than the CI-4+ oil choices in many fleets, and “better” depends on which performance aspects that you are emphasizing or valuing in a comparison. There is no doubt that TBN has been severely limited in the CJ’s, but there is often a difference in TBN stability/retention during use, which is determined not only by the TBN package design, but by other performance aspects of the oil. A lot of test data over the years has shown both that AMSOIL’s formulations are robust in both initial and retained TBN, while many leading oils have dropped lower in retained TBN.

    But there is obviously far more to oil performance than TBN, and ZDDP is not the only route to low wear rates. In terms of standard tests like the 4-ball wear test, NOACK, etc, AMSOIL CI+4 lubes have historically and consistently shown better performance than most other diesel oils on the market. It raises an eyebrow to occasionally see an oil equal an AMSOIL 4-ball wear scar size, and I can’t ever recall seeing any equal-weight, equal-spec oil with a smaller wear-scar than AMSOIL’s.

    The reason that AMSOIL is rarely shown in the mix in most comparative testing overviews is simple: it makes everyone else look mediocre. They are the undisputed First in Synthetics. And sometimes the AMSOIL performance gap is so large that it’s downright embarrassing. Lube industry insiders know that. The fact that AMSOIL is not sold on most store shelves appears to be a convenient excuse to not include AMSOIL in comparative testing.

    One of the things that the TDR comments point to is that many oil formulations are simply going to CJ-4 because they meet CI-4+ specs, and finding a CI-4+ ONLY oil could become difficult in the stores. Because of that, I think every fleet manager should take note that AMSOIL’s CI+4 lubes ARE available, and will remain available, and putting a pencil to some basic calculations and comparing test data will reveal that for pre-2007 engines they DO outperform EVERY CI-4+ or CJ-4+ oil on the market, whether considering overall technical performance, or overall dollar value. And with the increasing use of biodiesel blends, oil drain intervals WILL have to be shortened. See our diesel page for more info:

    Contact us to sign up for a free Commercial account, and you’ll get the lowest pricing available anywhere, backed by both expertise and support.

    We also have a Preferred Customer membership available for individual users that will get you genuine wholesale dealer pricing on your purchases.
    Information on Dealerships and Preferred Customer memberships is
    available here:

    Comment by autoengineer | November 11, 2007 | Reply

  3. Dealership and Preferred Customer info:

    Comment by autoengineer | November 11, 2007 | Reply

  4. […] CJ-4 Diesel Oils only for 2007 & later models – they’re NOT for earlier diesels! Mos… […]

    Pingback by 5w/40 Oil - Amsoil, Rotella, Mobil 1, Motorcraft - Page 4 - Diesel Forum - | January 7, 2011 | Reply

  5. Like AMSOIL states, any oil manufacture is free to prove AMSOIL wrong. So far all you hear are big claims that other oils are the best, but they know it’s not true. AMSOIL offers anyone to prove them wrong, so far no one will step up to prove them wrong, what does that tell you.

    Comment by Synthetic Oil Specialties | February 20, 2011 | Reply

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