From: Steve on 1 Dec 2008 13:43
> This was not a case of gunk, although the oil became black very quickly.
> The engine started using oil very badly soon after the Mobil I was used.
> That was the reason for the problem, not oil color.
YOU, I believe. I don't know about the other clown who claimed "black"
oil in a "new" Briggs engine. But even in your case I strongly suspect a
coincidence and not the oil, since a) there's nothing unique about a
Briggs engine that would rule out synthetic oil, and b) I've run
synthetic oil in a number of Briggs engines over the years with no
problem. Other than being air-cooled, its hard to think of an engine
LESS demanding of its oil than a Briggs. The things are so simple and
over-built for the power loading that you can just about run them on
anything halfway slippery. But you do have to change it regularly since
there's no filtration system.
From: Steve on 1 Dec 2008 13:46
> I can talk engineering with you all day long, but this is not a case
> where I
> am very open to "shoulda, coulda, and woulda".
Come on, YOU know better than to infer a trend from one data point. How
many other things could have happened to ruin that engine?
And last time I looked, Briggs has withdrawn any anti-synthetic
recommendations they had. Probably more a case of CYA than engineering.
From: Steve on 1 Dec 2008 13:53
Scott Dorsey wrote:
> Steve <no(a)spam.thanks> wrote:
>>> I also had an edger with a Briggs and Stratton engine and the oil turned
>>> black after one use. I knew immediately that the Briggs and Stratton engine
>>> I had then (don't know about newer ones) was not suitably built for
>>> synthetic oil (in the same way those Chevy Caprice and Crown Vic engines
>>> used in NYC taxis are not suitable for synthetic oil).
>> If you believe that particular engines are "not suitable for synthetic
>> oil," then there's no use trying to have an intelligent,
>> engineering-based discussion.
> In the case of small engines with splash-plate lubrication rather than
> an oil pump, the synthetic oils are NOT generally suitable for them. The
> better flow characteristics of the synthetics mean the splash plate cannot
> pick up enough oil.
If that were really true, then how do they meet the API specs for flow?
WAAAAY back in the dawn of synthetics, there were claims- possibly quite
true- about their lack of proper lubrication for the vertical surfaces
of some automotive engine thrust bearings, but that was addressed by the
oil makers 20+ years ago. If there were really that sort of difference
persisting to this day, it would show up lots of other places, not JUST
in air-cooled small engines. I just don't see it.
From: Steve on 1 Dec 2008 13:58
> Steve wrote:
>> jim wrote:
>>> As far as I know the type of dirt that gets into oil due to combustion
>>> byproducts is not going to be any different for synthetic oil.
>> That's true, and is a key part of this discussion. Too bad its being
>> discussed in terms of "synthetic" versus "conventional," because that
>> really doesn't matter. What DOES matter is the rest of the oil additive
>> package, in particular the compoenents that maintain the total base
>> number (TBN) and keep the oil from becoming acidic. You can have
>> synthetics with poor TBN control additive, and you can have
>> conventionals with good packages. Now *most* synthetics also happen to
>> be higher-end oils and have decent additive packages... but its not
>> BECAUSE they're synthetic.
> Yes, and "becoming acidic" is just one of the things that happens to oil as the
> miles go by. So what is the advantage of getting a good additive package that
> counteracts or slows down that inevitable deterioration versus just changing the
> oil more frequently to avoid the deterioration?
Like everything, its a trade-off. If every car owner went to a 6000-mile
versus the ridiculously short 3000 mile change interval, the savings in
crude oil or natural gas (the raw material for synthetic oils), the
reduction in energy required to produce the oil, and the reduced load on
the recycling infrastructure would be non-negligible. And since acid
increase starts the first time you turn the key, its better to use a
better additive package even if you KEEP your short drain interval, too.
On the other hand, buying an oil that CAN keep a reasonable TBN until
20,000 miles or some silly high number is counter-productive too, since
viscosity shift and solid (soot) contamination in automotive engines
with their rather poor filtration systems comes into play long before
then. From everything I've been able to gather, a change interval in
the 6000 to 9000 mile zone with good oil is a pretty reasonable trade
for the vast majority of car drivers out there.
From: Steve on 1 Dec 2008 14:07
C. E. White wrote:
> Reality check - what percentage of cars do you think are retired from
> service because of an engine "worn out" due to oil related wear (as
> opposed to failures related to the fuel, ignition, sensors, or other
> non-lubricated component)? I am guessing it is a very low percentage.
And I suspect the ones retired from service for all non-engine problems
combined is far smaller than those retired from service because the
owners just wanted something newer and flashier.