Date: Thu, 4 Oct 2007 12:43:44 -0700
Reply-To: mike <mwmiller@CWNET.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: mike <mwmiller@CWNET.COM>
Subject: Re: Mobil I ... negative..(from digest)
In-Reply-To: <002701c806a9$0f06c240$6cb2d8d1@laptop>
Content-type: text/plain; charset="US-ASCII"
Well, Mobil 1 was the most common oil in the failed engines but how many
engines were running Mobil 1 [not just failed engines but the whole
population of that type of engine] and how many ran other oils?
If 90% of the engines used Mobil 1 and 30% of the failed engines used Mobil
1 then that's a slight indication that the Mobil 1 wasn't the problem.
All this depends on the total number of engines and the number of failed
engines. If for example there were only 25 engines in the total population
you can't really say much statistically. Same game with the number of failed
engines but if the total population of engines was 1000 and there were 25
failures it would be a little stronger case statistically.
That's as I remember it but your mileage, and statistics, may vary.
Mike
On 10/4/07 10:07 AM, "Don Hanson" <dhanson@GORGE.NET> wrote:
> Hi,
> Perhaps it was a coincidence that Mobil One was the oil most often present
> in the motor-failures I was personally made aware of. For me, it is easier
> to eliminate the possibility of the same coincidence happening to me, again,
> by avoiding that particular type of synthetic oil.
> Porsche 928 motors are known to have a design weakness (prone to oil
> starvation, it was thought) in the #2/6 main bearing, and they often failed
> unless this weakness was addressed by cross drilling the crankshaft, by
> installation of an Accusump, or by 'dry sumping' the motor. When run at a
> track under prolonged left turn high G cornering, stock motors were prone to
> seizing up that particular bearing..Many instances of this were noted on our
> 928 Mailing list...Rennlist... One member undertook to document the type of
> oil being used at the time of these engine failures, and by far the most
> common oil was Mobil One synthetic..To me, that indicates Mobil One was
> perhaps the least effective lubricant...Most failures=Least effective...
> So yes, almost all of the 928 motor failures were proven to be
> lubrication-related. The two moto engines I blew were also bottom end
> bearing failures on relatively new motors..The Dayton Triumph was on it's
> first fill of "real" oil after being broken in exactly as prescribed by the
> Factory manual, the KTM had about one month of time on it and also blew out
> the bottom on what's widely regarded as a 'bullet-proof' very dependable
> motor.
> Is that "proof"? Heck no...but for me, it is close enough to proof to
> make me not use Mobil One and chance another coincidental motor blow up..
> I ain't saying it's bad, so don't go all defensive if you love the oil...I
> am saying I won't use it any more unless I can't find another brand in the
> proper weight, and if I do have to put some into a motor, I change it as
> soon as I can find another supply..
> Ciao.
> Don Hanson
> ----- Original Message -----
> From: "Dennis Haynes" <d23haynes57@hotmail.com>
> To: "'Don Hanson'" <dhanson@GORGE.NET>; <vanagon@GERRY.VANAGON.COM>
> Sent: Thursday, October 04, 2007 8:49 AM
> Subject: RE: Mobil I ... negative..(from digest)
>
>
>> Was any one of those failures proven to be lubrication related? I mean did
>> a bearing actually seize up because the correct viscosity, under proper
>> pressure and at proper temperatures oil actually failed to provide a
>> lubricant film? Or was it just a coincidence that Mobil 1 was there when a
>> valve spring broke or head gasket blew or a piston cracked while the
>> engine was being abused? Keep in mind that Porsches for many years are
>> known for their ability to keep mechanics employed. You still don't
>> regularly see 200,000 mile examples.
>>
>> Dennis
>>
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