Thanks Randall, that certainly is clear and explains the origins of the
folklore.
Will I get to meet you in person at Triumphest this year? Any other list
members going?
Bob
-------------- Original message ----------------------
From: "Randall" <tr3driver@comcast.net>
>
> > I'll pass on something I heard, don't know how true, but it was from
> > a usually reliable source; Since the advent of roller lifters, the
> > oil companies have been deleting the additive that keeps the cam from
> > wearing out on the straight lifter type of engine. The only oils
> > that still have it are those intended for diesel engines. There is a
> > a designator (CD or something like that-I can find out if anyone is
> > interested) that indicates the additive is there. The oil is
> > available at truck stops - Shell has been recommended to me. Anyone
> > know if there is any truth to the story?
>
> There's a tiny kernel of truth to that, but most of the above is very twisted.
> There is an additive containing zinc (zinc dialkyl dithio phosphate or
>something
> like that, ZDDP for short) that used to be found in higher concentrations in
>the
> better engine oils (like Valvoline). ZDDP really is something of a miracle
> additive, but since it's public domain, no one advertises it. It forms a
> microscopic film on the steel of the engine, that gets rubbed off first if
>there
> is metal-to-metal contact; thereby reducing wear.
>
> Unfortunately, zinc is a poison to catalytic converters, so the standards for
> the amount of zinc allowable in gasoline engine oils have moved downwards
> several times. As I recall, the current allowable standard is something like
> 1/3 as much zinc as Valvoline Racing oil used to have.
>
> However, AFAIK there are no such restrictions on diesel engine oil (and the CD
> designation indicates a diesel engine oil). That doesn't necessarily mean
>they
> have more ZDDP, only that they are allowed to. I just did a quick check,
> Chevron Delo 400 has .148% zinc while Valvoline racing now only has .13% ...
> hardly worth worrying about, IMO. I didn't find a zinc content for Shell
> Rotella, only the comment that it is going down in 2007.
>
> OTOH, full synthetic supposedly has a much higher film strength to begin with
> than conventional oil does, so should need the ZDDP less (since it only comes
> into play after the oil film breaks down). Those big truck oils cost as much
>as
> full synthetic, and after all have additive packages for diesel rather than
> gasoline (they were already separate oils before the restrictions on zinc came
> about). So while I can't prove which one is better, I plan to stick with
> Valvoline full synthetic.
>
> Randall
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