Re: Engines that are prone to sludge

HLS wrote:
> 
> <johngdole@[EMAIL PROTECTED]
> wrote in message 
>
news:5987752c-4f1d-4983-866a-23127cf4257e@[EMAIL PROTECTED]
> The 7500 mile interval is not correct. In 2004 Toyota has lowered that
> interval down to 5000 for ALL Toyota/Lexus engines while GM and Honda
> pushed it to 12,000 miles during this period.
> 
> When I started to buy a Toyota, I asked about that sludging condition.  
> They indeed
> recommended a shorter than original change interval, and told me that in

> every case
> that there had been a problem, the owner had not maintained the 
> recommended interval.

I don't buy that - I'd take that with a grain of salt.  People make that 
kind of statement often based on very little more than thin air.  There 
is no question that some engines are way less tolerant of stretched out 
maintenance than others.  Other factors come into play, like if the 
vehicle sees a lot of short-trip and/or stop and go driving vs. mostly 
highway commutes.  IOW - with certain engines, long oil change intervals 
may not do it in if most of its driving is daily highway commutes, but 
give it OK change intervals, and do mostly short-trip/stop-and-go, and 
it will likely fail.  Combine longer change intervals with short trip 
and stop and go, and it will surely fail.  Another engine could tolerate 
both without a problem.

> BUT, there were also some issues with the PCV system that were discussed

> on this
> newsgroup that may have also influenced the sludging.  IIRC, they had 
> reduced the
> ventilation action and that could well influence oil sludging.

I have a theory that there was technical discussion within the industry 
where, in the lab and road testing, they were seeing some measurable 
incremental pollution control advantage in narrowing down crankcase 
venting and oil drain holes (the sort of thing that papers are published 
on in technical societies), so several companies decided to try it out 
without really knowing the longer-term effects - IOW, unintended 
consequences, being prone to sludging being one of the unintended 
consequences.  IOW - a lesson learned.

> I believe that our 2007 has a longer change interval than 5000 miles, 
> but I never let it
> go so long anyway.

Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my 
address with the letter 'x')