A3/B4 in HDEO application, what would go wrong?

[OM617YOTA]

Alrighty, the PCEO in a Babymax thread got me thinking. Partly I'm bored, partly I'm genuinely curious.

Say someone has stock of a solid Euro Xw40 A3/B4, and HDEO just isn't available for whatever reason. Maybe they're too lazy to go to the store, or maybe it's the end of the world and they're sitting on 10,000 gallons of diesel fuel and a pile of Euro oil but no HDEO. Hypothetical, exact reason doesn't matter for the purpose of this exercise. Time to change oil in their Cummins/Powerstroke/Duramax.

Assume the engines are pre-emissions or deleted, high saps doesn't matter.

What would go wrong using A3/B4 in an HDEO application? Confident the engine won't blow up right away or even after significant miles, but what would happen? Oil shear down/deplete additives faster than HDEO and require shorter OCI?

The Mobil Euro 0w40 A3/B4 I have on hand is also CF rated. Looks like CI/CJ/CK ratings are mostly to do with emssions, so is that it? Do they actually protect any better than a CF, or are emissions it?

 

[fantastic]

The Mobil Euro 0w40 A3/B4 I have on hand is also CF rated. Looks like CI/CJ/CK ratings are mostly to do with emssions, so is that it? Do they actually protect any better than a CF, or are emissions it?

Test requirements change so a CF is quite old & considered obsolete but understanding that's not what this oil is positioned for. An HDEO has to meet different test requirements than a light duty oil does. A light duty A3/B4 could mean lower oxidation stability, more oil consumption, lower HTHS on some grades, etc.

If you don't care or need emissions friendly oil & want the best chance at wear protection a 15w-40 or 5w-40 CK-4 HDEO is a good choice in this engine. I think GM did great on their 6.6 Duramax over the years but think they fell short on the 3.0L oil requirements. IMO a 0w-20 should not be put in this engine. I think just about any grade higher would be better than that. So, if the oil apacalypes happens then at least grab any 30 grade available. Maybe you'll get lucky & find truck & SUV at least at the bare minimum.

Yes, that 0w-40 would be better too.

Here's the thread mentioned:

Z

Thread 'Using Euro PCEO in 3.0L babymax?'

May 13, 2026

I recently traded in my 2500 gasser and went back to the babymax. I still have a couple oil changes worth of HPL's 5W-40 Euro oil and was wondering if it would be alright to use it for my early break-in oil changes, no more than 1k miles.

It's ACEA A3/B4 and Porsche A40 spec'd. I know B4 is more of a pre-emissions diesel thing, I was just hoping to not have to sell it off. My plan is to go to Amsoil's European AFL 5W-40 for my regular oil changes after break-in.

• Z28racecar

• 

 

[OM617YOTA]

Test requirements change so a CF is quite old & considered obsolete but understanding that's not what this oil is positioned for. An HDEO has to meet different test requirements than a light duty oil does. A light duty A3/B4 could mean lower oxidation stability, more oil consumption, lower HTHS on some grades, etc.

If you don't care or need emissions friendly oil & want the best chance at wear protection a 15w-40 or 5w-40 CK-4 HDEO is a good choice in this engine. I think GM did great on their 6.6 Duramax over the years but think they fell short on the 3.0L oil requirements. IMO a 0w-20 should not be put in this engine. I think just about any grade higher would be better than that. So, if the oil apacalypes happens then at least grab any 30 grade available. Maybe you'll get lucky & find truck & SUV at least at the bare minimum.

Yes, that 0w-40 would be better too.

Here's the thread mentioned:

Z

Thread 'Using Euro PCEO in 3.0L babymax?'

May 13, 2026

I recently traded in my 2500 gasser and went back to the babymax. I still have a couple oil changes worth of HPL's 5W-40 Euro oil and was wondering if it would be alright to use it for my early break-in oil changes, no more than 1k miles.

It's ACEA A3/B4 and Porsche A40 spec'd. I know B4 is more of a pre-emissions diesel thing, I was just hoping to not have to sell it off. My plan is to go to Amsoil's European AFL 5W-40 for my regular oil changes after break-in.

• Z28racecar

• 

Appreciate the thoughts.

Just to be clear, I wasn't asking about the 3.0 Duramax or commenting on that thread specifically. I was asking what would happen to a 6.6 Duramax, 5.9/6.7 Cummins, or 7.3/6.0/6.7 Powerstroke if an A3/B4 was used instead of CK4, and what exactly the differences between A3/B4 and CK4 are.

 

[fantastic]

Appreciate the thoughts.

Just to be clear, I wasn't asking about the 3.0 Duramax or commenting on that thread specifically. I was asking what would happen to a 6.6 Duramax, 5.9/6.7 Cummins, or 7.3/6.0/6.7 Powerstroke if an A3/B4 was used instead of CK4, and what exactly the differences between A3/B4 and CK4 are.

An A3/B4 oil isn't up to the same testing standards so I'd assume the easy answer is wear would increase along with the other parameters I previously mentioned.

 

[Japanese]

What would go wrong using A3/B4 in an HDEO application? Confident the engine won't blow up right away or even after significant miles, but what would happen?

I was asking what would happen to a 6.6 Duramax, 5.9/6.7 Cummins, or 7.3/6.0/6.7 Powerstroke if an A3/B4 was used instead of CK4

Nothing would happen because A3/B4 oils are also suitable for diesel engines. And specifically for gasoline and diesel turbo engines. If the car/truck has DPF then ACEA C3 oils are used. That's all. Actually, if I had diesel car/truck I would run A3/B4 oil over HDEO. All

Understanding Oil Standards ACEA Specifications
All A/B oils are stable, stay-in-grade lubricants, used by gasoline engines and light-duty diesel engines. All products belonging to this category are utilized in high-performance petrol engines and light-duty diesel engines.

• A3/B4 oils are used in high-performance and direct-injection diesel engines. They can also be used instead of A3/B3-grade oils.


ACEA Service Classifications
• A3/B4
For use in direct injection diesel engines where special oils may be required, but also suitable for applications described under A3/B3.

It's interesting that DPF/DEF are not mentioned under the API CK-4 standard:
API Diesel C Categories

Use ACEA A3/B4 or C3 (DPF/DEF friendly) for diesel passenger cars, trucks and vans. Use API CK-4 for diesel construction machinery, commercial trucks and vehicles. That's how I understand it.

An A3/B4 oil isn't up to the same testing standards so I'd assume the easy answer is wear would increase along with the other parameters I previously mentioned.

Tell that to the German engineers who spec'd all German turbo diesel cars and SUV's for ACEA C3 oil, which could be considered the GPF/DPF friendly version of the A3/B4 oils.

Mobil 1 FS Euro 0W-40 - ACEA A3/B4

Applications​

• Mobil 1™ FS European Car Formula motor oils are recommended by ExxonMobil for all types of vehicles, including high-performance turbo-charged, supercharged gasoline and certain diesel multi-valve fuel injected engines found in passenger cars, SUVs, light vans and trucks.

Mobil 1 ESP x4 0W-40 - ACEA C3

Applications​

• Mobil 1 ESP motor oils are recommended by ExxonMobil for all types of vehicles, including high-performance turbo-charged, supercharged gasoline and certain diesel multi-valve fuel injected engines found in passenger cars, SUVs, light vans and trucks.

Mobil 1 ESP 0W-30 - ACEA C3

Applications​

• Mobil 1 ESP motor oils are recommended by ExxonMobil for all types of vehicles, including high-performance turbo-charged, supercharged gasoline and certain diesel multi-valve fuel injected engines found in passenger cars, SUVs, light vans and trucks.

 

[fantastic]

Nothing would happen because A3/B4 oils are also suitable for diesel engines. And specifically for gasoline and diesel turbo engines. If the car/truck has DPF then ACEA C3 oils are used. That's all. Actually, if I had diesel car/truck I would run A3/B4 oil over HDEO. All

Understanding Oil Standards ACEA Specifications
All A/B oils are stable, stay-in-grade lubricants, used by gasoline engines and light-duty diesel engines. All products belonging to this category are utilized in high-performance petrol engines and light-duty diesel engines.

• A3/B4 oils are used in high-performance and direct-injection diesel engines. They can also be used instead of A3/B3-grade oils.


ACEA Service Classifications
• A3/B4
For use in direct injection diesel engines where special oils may be required, but also suitable for applications described under A3/B3.

It's interesting that DPF/DEF are not mentioned under the API CK-4 standard:
API Diesel C Categories

Use ACEA A3/B4 or C3 (DPF/DEF friendly) for passenger cars, trucks and vans. Use API CK-4 for construction machinery, commercial trucks and vehicles. That's how I understand it.


Tell that to the German engineers who spec'd all German turbo diesel cars and SUV's for ACEA C3 oil, which could be considered the GPF/DPF friendly version of the A3/B4 oils.

Mobil 1 FS Euro 0W-40 - ACEA A3/B4

Applications​

• Mobil 1™ FS European Car Formula motor oils are recommended by ExxonMobil for all types of vehicles, including high-performance turbo-charged, supercharged gasoline and certain diesel multi-valve fuel injected engines found in passenger cars, SUVs, light vans and trucks.

Mobil 1 ESP x4 0W-40 - ACEA C3

Applications​

• Mobil 1 ESP motor oils are recommended by ExxonMobil for all types of vehicles, including high-performance turbo-charged, supercharged gasoline and certain diesel multi-valve fuel injected engines found in passenger cars, SUVs, light vans and trucks.

Mobil 1 ESP 0W-30 - ACEA C3

Applications​

• Mobil 1 ESP motor oils are recommended by ExxonMobil for all types of vehicles, including high-performance turbo-charged, supercharged gasoline and certain diesel multi-valve fuel injected engines found in passenger cars, SUVs, light vans and trucks.

I don't even know where to start here. Where does Mobil say to use this in an application where it isn't suitable? Even from the Mobil statements you quoted are using "Certain" language. Does "Certain", to you, mean any diesel engine application?

Nothing would happen? That is quite a claim.

Tell us why HDEO exists ?

 

[Japanese]

Tell us why HDEO exist ?

I said already - for commercial construction trucks and machinery. Do you know how much oil are their oil sumps? In the States the diesel vehicles are mostly commercial. There are just a handful of full size trucks with 6.0-7.0L engines.

Nobody in Europe uses HDEO in their turbo diesel passenger car, van or truck, especially German ones. They run either ACEA C3 or A3/B4 (if there is no DPF). Why is that?
In Europe every other car is a turbo diesel from 1.4L to 4.0L engines. Diesel fuel is cheaper over there and cars with those engines are much fuel efficient than gasoline ones.

I cannot understand why do you think ACEA rating is lower than API and that the wear would increase? Those two standards may overlap or even the ACEA could be higher.

An A3/B4 oil isn't up to the same testing standards so I'd assume the easy answer is wear would increase along with the other parameters I previously mentioned.

How do we know that and what is based on?

 

[fantastic]

I said already - for commercial construction trucks and machinery. Do you know how much oil are their oil sumps? In the States the diesel vehicles are mostly commercial. There are just a handful of full size trucks with 6.0-7.0L engines.

Nobody in Europe uses HDEO in their turbo diesel passenger car, van or truck, especially German ones. They run either ACEA C3 or A3/B4 (if there is no DPF). Why is that?
In Europe every other car is a turbo diesel from 1.4L to 4.0L engines. Diesel fuel is cheaper over there and cars with those engines are much fuel efficient than gasoline ones.

I cannot understand why do you think ACEA rating is lower than API and that the wear would increase? Those two standards may overlap or even the ACEA could be higher.

How do we know that and what is based on?

I don't claim ACEA is "Lower" than API. I stated that A3/B4 has not been tested to the same standard of tests. You are in fact saying there would be no wear if A3/B4 was used continuously in an HDEO application so show us the rest of where your information is coming from. I made an assumption about wear but your saying something as a matter of fact. Show us the tests you claim "Nothing" will happen b/c to you an A3/B4 is 100% suitable for an HDEO application. I'm sure you have information to back it up right? If not just say so & the board can have accurate information. Doesn't matter if European market uses "HDEO" or not, what matters is they use what's specified in their manual so there isn't a concern in language there.

 

[Japanese]

Show us the tests you claim "Nothing" will happen b/c to you an A3/B4 is 100% suitable for an HDEO application. I'm sure you have information to back it up right? If not just say so & the board can have accurate information.

Doesn't matter if European market uses "HDEO" or not, what matters is they use what's specified in their manual so there isn't a concern in language there.

How many more facts do you want? I just cited two sources (one US and one AUS) that say ACEA A3/B4 is diesel engine oil. And then cited three different pages of the Mobil website. The thing is that most oils that are rated A3/B4 and specifically Mobil 1 FS 0W-40 also cover and Mercedes-Benz MB 229.51 tests. Write on Google or ask AI what tests oil rated MB 229.51 cover. I can tell you only that they are about 35 teest (both bench and real driving conditions tests) in various engines, both gasoline and diesel. Those engines include Ford (V8), GM (V6), MB (4 cyl. and 5 cyl. diesel), VW (4 cyl. diesel), Toyota engines (4 cyl.) and Peugeot. Cam wear at various temp. (cold and hot) is measured, sludge and soot are also monitored very closely.

The oil that the OP asks about (Mobil 1 Euro 0W-40 A3/B4) covers MB 229.5 which is one of the most stringent oil test for both gasoline and diesel engines. Min. HTHS for those oils is 3.5 cP and TBN should be no lower than 10.

What oils is specified in the OP owner's manual and what engine bench test those oil cover?

 

[rollins.]

Nobody in Europe uses HDEO in their turbo diesel passenger car, van or truck, especially German ones. They run either ACEA C3 or A3/B4 (if there is no DPF). Why is that?

This is not quite true. Whoever interpreted the available info properly ...or even bothered to look in the onwer's manual used HDEO too .
Some vans with engines used in passenger cars too came with HDEO as factory-fill. If the owners overlooked this fact and refused to pay attention to the options the manuafcturer explicitly allowed/recommended, well- their choice.

Whoever put in the effort to obtain for example some Low-SAPS 5w-30 HDEO with 228.51 for their PC/van diesel (whatever the make and AT equipment ) have been pretty content with the results.

As you can see , the approved HD specs are there - 228.3, 228.5,228.51 :

2024 Vito Owner's manual :

2016:

etc.


Some online "oil guides" offer some of their HDEO's as an option too. Problem in Europe is the scarcity of synthetic HDEO in 0/5w-40 grades. Also, annoyingly HDEO's come usually in 20l. -and above packaging with some dual rated mineral and semi-syn HDEO's still offered in 4l. & 5l. jugs .

I have yet to see an OEM allowing ACEA A3/B4 or C3 oil even for an emergency top-up in their HD equipment calling for 228.x/.xx , CH-4...CK-4 or whatever HD spec .

European Car manufacturers used to perscribe HDEO oils for their PC and lighter-duty diesel engines (there weren't that many). The owner would use the same BP Vanellus or Essolube XD or Shell Rimula API CC or CD the heavy transport used .
This begins to change with the proliferation of the small diesels, the formation of the CCMC (the ancestor of ACEA)and the oil categories they introduce (a certain product could carry one or more CCMC specs) . Most importantly, OEM specifications emerge . API certifications in the Euro context become less and less relevant already > 4 decades ago.Now many Euro UHPD (long drain,high-SAPS) oils lack API certifications or have an obsolete one ,like API CF - it is the OEM spec that matters.

IMO the 3.0D-max would do fine (even longer-term) on 229.5 . I would not be that brave on the other ones ( I am really curious how 229.5 would perform against 228.5 of the same SAPS levels in a modern ...and in a 40 years old 12--- 16 liter mechanically controlled diesel) .

 

[fantastic]

How many more facts do you want? I just cited two sources (one US and one AUS) that say ACEA A3/B4 is diesel engine oil. And then cited three different pages of the Mobil website. The thing is that most oils that are rated A3/B4 and specifically Mobil 1 FS 0W-40 also cover and Mercedes-Benz MB 229.51 tests. Write on Google or ask AI what tests oil rated MB 229.51 cover. I can tell you only that they are about 35 teest (both bench and real driving conditions tests) in various engines, both gasoline and diesel. Those engines include Ford (V8), GM (V6), MB (4 cyl. and 5 cyl. diesel), VW (4 cyl. diesel), Toyota engines (4 cyl.) and Peugeot. Cam wear at various temp. (cold and hot) is measured, sludge and soot are also monitored very closely.

No where does it say to use a European oil in the owners manual of these HD engines. If your source is AI that's the problem. If you want to double down about A3/B4 oils being equivalent to an HDEO you'll need to show us more than an AI search. You seem to ignore the "Certain" language on Mobil's site too.

The oil that the OP asks about (Mobil 1 Euro 0W-40 A3/B4) covers MB 229.5 which is one of the most stringent oil test for both gasoline and diesel engines. Min. HTHS for those oils is 3.5 cP and TBN should be no lower than 10.

What oils is specified in the OP owner's manual and what engine bench test those oil cover?

"Stringent" in one application may be null & void in another. So now that you believe a light duty MB 229.5 covers all American made HD applications & "nothing will happen" get us the tests perimeters that show us proof that satisfies the Heavy Duty engine requirements. You've still not provided ANY concrete evidence a European oil is all that's needed. You're even asking what the manuals say in the HD trucks. Do you have any idea of what these engines need?

I'll repeat for the rest of the board... You've not shown anything that using an ACEA European oil for an HD applications will provide "Nothing will happen" for wear etc. You're Mobil quotes spell out "Certain" applications & using AI as a source is a fools game.

 

[dlundblad]

A guy here (I can never remember who it is) uses an A3/B4 in his Kubota diesel generator. The UOA’s look great.

What exactly is heavy duty vs light duty anyways? What is working harder? A ~100 hp diesel Jetta full of people or a diesel F350? The former would require the A3/B4.

 

[fantastic]

A guy here (I can never remember who it is) uses an A3/B4 in his Kubota diesel generator. The UOA’s look great.

What exactly is heavy duty vs light duty anyways? What is working harder? A ~100 hp diesel Jetta full of people or a diesel F350? The former would require the A3/B4.

Does a Jetta need to pull 30,000 lbs? If you tried it would you want to be using an HDEO or ACEA A3/B4?

There are differences in the application itself. Obviously, the oil needs to work harder in different areas to maintain the interval while protecting critical areas of the engines they're designed to go in.

A Diesel generator could very well be fine on a European oil if that's what's designed for. Many European passenger vehicles go 100,000's of miles on A3/B4 so no one here can say it's "bad" oil but it's certainly not it's intended purpose to be put into HDEO applications. There are attributes to a Commercial oil that separates it from the Light duty European standards. To start with they don't test an HDEO on a Jetta & they don't test a European oil on an F-350 6.7L engine either. Oil is designed for the application's they serve. I've mentioned a few of the differences already.

 

[dlundblad]

Does a Jetta need to pull 30,000 lbs? If you tried it would you want to be using an HDEO or ACEA A3/B4?

There are differences in the application itself. Obviously, the oil needs to work harder in different areas to maintain the interval while protecting critical areas of the engines they're designed to go in.

A Diesel generator could very well be fine on a European oil if that's what's designed for. Many European passenger vehicles go 100,000's of miles on A3/B4 so no one here can say it's "bad" oil but it's certainly not its intended purpose to be put into HDEO applications. There are attributes to a Commercial oil that separates it from the Light duty European standards. To start with they don't test an HDEO on a Jetta & they don't test a European oil on an F-350 6.7L engine either. Oil is designed for the application's they serve. I've mentioned a few of the differences already.

My point was the oil in the Jetta (small engine) is likely working pretty hard.

 

[fantastic]

My point was the oil in the Jetta (small engine) is likely working pretty hard.

Possibly but I figured those engines last quite a while on their oils? I don't know much about VW though.

 

[Klutch9]

I actually wonder this too. Has anyone compared the A3/B4 tests and requirements to some of the API heavy duty diesel tests? I wonder if it’s a case that both oils would do well, they are just tested to different (albeit both stringent) standards. A lot of diesel engines actually have a relatively low specific output compared to gasoline engines. They do work harder in certain applications, but the engine isn’t always as stressed.

 

[fantastic]

I actually wonder this too. Has anyone compared the A3/B4 tests and requirements to some of the API heavy duty diesel tests?

I've gone over the HDEO testing here & there over the years. You can find some from the additive companies. If European oil was all that was needed there would be no need for big $$$$$$ invested in testing, formulating, & licensing for HDEO applications.

 

[dlundblad]

I've gone over the HDEO testing here & there over the years. You can find some from the additive companies. If European oil was all that was needed there would be no need for big $$$$$$ invested in testing, formulating, & licensing for HDEO applications.

An American company wouldn’t suggest a Euro spec oil.

 

[fantastic]

An American company wouldn’t suggest a Euro spec oil.

You understand... I wish they all did.

 

[burbguy82]

I would not run Mobil 1 0w40 in my Kubotas