I had my car serviced yesterday and the engine has now been filled with
Comma oil. To confirm the grade was correct against the handbook I checked
the Comma website.

I notice they sell 4 "varieties" of 5W-30 fully synthetic. They have
"Syner-Z", "Protech", "Longlife" and the wonderfully named "Prolife". There
are also 3 varieties of FS 5W/40 plus several semi alternatives. (There's no
direct link to the page other than going via their home page
www.commaoil.com).

Not only that, but when looking up different cars with the same (diesel)
engines, there is no clear consistency.

Kia ("Syner-Z"), Hyundai ("Longlife")
Peugeot ("Protech"), Ford ("Xtech" semi), Citroen ("Dlite" - 10W/40 semi)
Fiat/Alfa ("Protech"), Vauxhall ("Syner-D" 5W/40)
VW group ("Prolife")
Mini/BMW ("Syner-Z")
Nissan ("Eurodiesel" 15W/40 semi), Renault ("Diesel PD" 5W/40 semi)

So, by how many microseconds would an engine's life be shortened if it was
given a few doses of Prolife instead of Longlife?

Looking further at Castrol, it's notable that the Nissan moves to 0W/30. And
whereas the Mini also moves to 0W/30, Kia goes up to 5W/40. Illogical.

Is there really any difference in this stuff apart from the packaging?

DavidR wrote:
If they have different A B or C numbers after ACEA, yes.

"Nick Finnigan" <nix (AT) genie (DOT) co.uk> wrote

Or manufacturer specification numbers. The oldest VW specs cover almost all
half decent oils on sale today. The newest ones are £30 a litre magic brews.

"Nick Finnigan" <nix (AT) genie (DOT) co.uk> wrote

....other than for the fact that they say they meet certain manufacturer's
specs and the application guide then suggests something different. And then
there are the identical engines under bonnets carrying different badges.

DavidR wrote:
Eh?

"Nick Finnigan" <nix (AT) genie (DOT) co.uk> wrote
.... for instance, the application guide suggests the oil poured into Citroen
is not the same as recommended for a Peugeot. Or for the Peugeot made
engines fitted in Fords. Did you not see my original post?

DavidR wrote:
Yes. I still see no relevance in your responses to my post:

"If they have different A B or C numbers after ACEA, yes."

"Nick Finnigan" <nix (AT) genie (DOT) co.uk> wrote
Well, yes there's some guff after ACEA bit. But if there is material
difference in the product, it seems pretty immaterial to the engines.

DavidR wrote:
For a 53 vehicle, my handbook suggests A1 and A5 give better mpg, but A3
is still OK for stupidly long intervals between changes. If you are going
to change every 9,000 miles anyway, then A2 /B4 is fine. So different oils
can each be 'recommended' for the same engine, in different applications.