Change oil soon (& then some)

[Greg Hermann]

>You're right Shannen--it's a thermal issue. The other
>is under computer models, the reduced oil viscosity
>pumps easier and "theoretically" provides better
>fuel economy--less pump HP parasitic losses.
>
>Lyndon.

>>
>> Better grades of oil have allowed reduced engine clearance
>> specs.  In turn, reduced engine clearances require "thinner"
>> oil.  Oil of too high viscosity can cause the bearings to
>> burn out.  I don't know whether it's th inability of the oil
>> to carry heat away fast enough, or the inability of th oil
>> to provide adequate lubrication.

Thinner oil will yield a higher volume flow rate, and thus carry heat off
more effectively. Thicker oil will generally give a higher film strength
under extreme conditions-although some of the synthetics are an exception
to this.

Moderately tighter bearing clearances than what is traditional, together
with a high volume pump and thinner oil can be a great compromise--& keep
the bearings real cool--but the factories are going with really tight
clearances, thin oil, and a lower volume pump so as to keep the parasitic
HP down too. In this kind of a set-up--heavier oil will lead to too little
flow of oil through the bearings (as a coolant) and things will fry.

>>
>> This can also happen in aluminum manual transmission
>> gearboxes when the required ATF has been unknowingly
>> replaced with traditional gear oil.

Usually only in the ones with a teensy little oil pump with a "microscopic"
drive!

NON-EP type gear oils will generally be OK in most trannies--the sulphur
and chlorine based additives in the  EP (hypoid) type gear oils will
corrode some parts in many manual trannies, though.

Never seen ZDP additive hurt anything. And--oh BOY --does it give
protection under extreme pressure conditions!!

Greg
>>
>> Shannen


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