Mixing oil weights and 10w40

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3 total messages Started by ems Tue, 31 Dec 1985 19:41

#361

Author: ems
Date: Tue, 31 Dec 1985 19:41

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I have received mail from several folks on the question of
mixing different vicosities of oil.  The consensus?  There is
no way of predicting the final outcome.  The viscosity is a
product of the oil base and additives.  Even from a single
manufacturer mixing different bases and additives results
in a new, unique, mixture that can be measured but not
predicted ...

Looks like I will have to look for another synthetic 10w40 ...
I know Amsoil used to make one.  Do they still?  Are there
other 10w40 synthetics that have done a good job for you?

Thanks for the replies,
-- 
E. Michael Smith  ...!{hplabs,ihnp4,amd,nsc}!amdahl!ems

This is the obligatory disclaimer of everything.

Re: Mixing oil weights and 10w40

#542

Author: Joe Weinstein
Date: Tue, 07 Jan 1986 18:28

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Hi.	Some facts about oil viscosity and mixing.

	1 - The effect of one viscosity oil on another is
	not linear! A lower viscosity oil will bring down
	the viscosity of the mix even in small percentages.
	Contrastingly, You have to add so much thick oil to
	thicken a mixture that you would need bathtubs and
	bathtubs full of 40 wt. to bring a quart of 30 wt.
	up to near 40 wt. You can test this with a cup of
	30 wt. and some 3-in-1.
	This means that topping up with a heavier oil is OK.
	As soon as they mix the viscosity will be what you had
	before.

	2 - The listed viscosities on cans are in fact ranges
	which can OVERLAP! One dealer's 30 wt. might be sold
	as 40 wt. by another!

	3 - Oil breaks down with ( time X high temperature ).
	A major factor in the temperature of an oil in an
	engine is the viscosity. A thicker oil gets hotter
	owing to shear forces than a thinner one. All oils
	break down at the same temperature. Therefore you should
	use the lightest oil recommended by the engine manufacturer.
	Especially after break-in where surfaces are smooth.

	The additives are more important than the viscosity.
	Use only the best grade ( SF ). Also, molybdenum add ins
	work to coat surfaces and protect them during start-up 
	before the circulation system gets oil there. Start-ups
	account for a lot of the wear of a broken-in engine so
	moly is a good bet.

	Joe Weinstein

Re: Mixing oil weights and 10w40

#553

Author: henning
Date: Sat, 11 Jan 1986 19:05

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****                                                                 ****
From the keys of Steve Henning, AT&T Bell Labs, Reading, PA mhuxl!smh

> 	3 - Oil breaks down with ( time X high temperature ).
> 	The additives are more important than the viscosity.
> 	Use only the best grade ( SF ). Also, molybdenum add-ins
> 	work to coat surfaces and protect them during start-up 
> 	before the circulation system gets oil there.

An oil execuative told me that the multi-viscosity additives break
down ususlly in the first 1000 miles.  He prefered single weight
oils since he knew what his viscosity was for at least 2000 miles.

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