Tim wrote, or sneered:
> Tribal knowledge until someone comes up with DATA. Or even DATUM.
> Don't hold your breath.

From the web, so must be true:
> There is one main cleaning ingredient in all fuel injector cleaners,
> it's a long, quadruple word score-kind of word, it's acronym is PEA.
> Due to chemical reactions, they have to disclose how much PEA content
> is in any given product on an MSDS sheet. Despite how much people love
> Lucas Upper Cylinder Lubricant fuel injector cleaner, it has the
> lowest concentration of PEA <5% by volume according to Lucas' own
> admission. Seafoam has no PEA (IIRC) just petroleum distillates and
> lighter fluid. Gumout Regane and Redline SI Fuel Injector Cleaner
> both have the highest concentration of PEA ~40% by volume.

Even truer is my memory:  When I bought my '76 (new) FI was
pretty new on buses.  When it ran roughly, VW recommended a BG
(brand) additive to clean the injectors.  It worked.

When I bought my '81 (new) VW's position was that no cleaner
was needed because injector design had improved and gasoline
additives had improved because of the conversion to FI.

I've never needed injector cleaners in my '81 with 150K mi,
my Syncro with 155K mi or my 911 with 123K miles, all with
original injectors.

I don't know anything about "injector cleaning" vs "fuel system
cleaning."  Now, back to arguing about brands and gas grades....

Richard