Potential evidence Mobil Clean 5K a Group III oil

Not open for further replies.
Jul 2, 2007
Okay, so I'm obsessed a little about whether Mobil Clean 5000, one of the lowest cost oils on the shelf, could have a Group III base stock hiding in the bottle, since it has been hinted at here before.

Found a potential clue. As previously mentioned, the MSDS for MC5000 describes the fluid as Base oil severely refined (page 6 under heading "Contains"):


The key is in knowing how XOM interprets both the term "severely refined" (as relating to mineral oil) and what they consider as synthetic. Do they follow the post lawsuit guideline and allow the term synthetic to encompass Group III mineral oil (hydrocracked) or do they still adhere to the pre-lawsuit protocol where only Group IV PAO and above is deemed as synthetic? I found this page on their Australian website that indicates they only consider Group IV PAO and above to be worthy of being called synthetic:


About 1/3 to 1/2 down the page there are four paragraph headings titled Hydroprocessed Oil, Severe Hydroprocessed Oil, Semi-Synthetics, and Synthetics. This appears to give insight into how XOM classifies base oils.

So from this, it would seem to follow that the "Contents" description in the MC5000 MSDS as Base Oil Severely Refined would indicate Severe Hydroprocessed as described on the Australian XOM page, which would be Group III.

Not an outright definitive statement encompassing MC5000's base oil, but given the above it makes sense that XOM would call MC5000 a conventional oil even if it is Group III, i.e. severely hydroprocessed.
Not that Mobil Clean 5000 is a bad oil, but I think its an inexpensive oil, and nothing Group III about it. If there was anything close to semi-synthetic about it they wouldn't hide it. It would be all over the label. JMO
Plus the fact that Mobil tech services, over the telephone says it is not synthetic, does not contain synthetic, "regardless of your definition of synthetic." No GP III or GP IV.
But how do we get around the MSDS statement that MC5000 is Severely Refined oil? By the logic of the cited XOM webpage, Severely Refined = Severely Hydroprocessed. Severely Hydroprocessed = Group III, yes?
The question is does severely refined mean severely hydrocracked?

Hydrocracking is a refinery process where the crude oil is subjected to high temperatures and high pressures in the presence of hydrogen. This not only rearranges the molecule to make them more stable, but also removes impurities. Most motor oils in future will use Hydrocracked base oils. If the hydrocracking process is severe enough, it creates a synthetic molecule.

Trust me if XOM could call it legally call it a synthetic of any kind, semi or otherwise they would. JMO
Grp II oil is severely hydrotreated.

A Grp III is severely hydroprocessed too butit starts with better feedstock or is processed more intensively or repeatedly to create a base oil with a VI greater than 120. The energy and materials to make a grp III are the reason it is more expensive. They both eat up Platinum catalyst, hydrogen feed and process heat.

Grp 1 was traditionally Clay treated. and or solvent dewaxed
Last edited:
Originally Posted By: Throckmorton
Do a little searching on the site and you'll see that Mobil 5000 uses a grp III base.

Yes, I've seen the threads, some of which refer back to an older thread by a user Carpy.

I felt as though the info on the MSDS coincided with the info on the Australian page and the "Severe" terminology seemed to point to Group III.
If you look up GP II, it says:
CAS 64742-54-7
Distillates Petroleum
Hydrotreated Heavy Paraffin

If you look up GP II+, it says:
CAS 64742-54-7
Distillates Petroleum
Hydrotreated Heavy Paraffin

If you look up GP III, it says:
CAS 64742-54-7
Distillates Petroleum
Hydrotreated Heavy Paraffin

Some companies are proud to talk about their base being isomerized dewaxed rather than solvent dewaxed. Some companies are proud to talk about their base being Hydrotreated Heavy Paraffin.(sounds really impressive) Some like to use terminology like severely refined.

Why don't you just call Mobil like I did and ask their tech services. They don't like to talk about base oil groups but they were quick to tell me 5000 was pure conventional, no synthetic by any definition.
Originally Posted By: Bryanccfshr
Carpy has been discredited.

I did not know this.
That is OK, It was long ago. From time to time someone will show up spreading misinformation, unfortunately those post and the misinformation are still in the archives. If you read those post and weren't here at the time I can see how it can sound like a legitimate post. He was eventually banned.
Not open for further replies.