on 11/7/03 3:08 PM, Charles & Peggy Robinson at ccrobins@ktc.com wrote:
> Max Heim wrote:
>
>> Because multi-grade oil DIDN'T EXIST when these were designed, so they were
>> obviously NOT designed with it in mind.
>
> I'm skeptical about that, Max. Seems like I could get 10W-30 Havoline
> in '59 when I drag racing a '57 Chevy in A-Stock class. When was the LH
> overdrive first produced?
I dunno, but I would guess the basic design dates from the early 50s? I
admit I wasn't up to changing oil in 1959...
>
>> The fact that BL, after the fact,
>> included it in their recommendations doesn't mean they understood the
>> issues; judging from their track record, they probably just took the
>> easiest/cheapest way out, or jumped on the new trendy bandwagon, or just
>> figured it didn't matter.
>
> I don't believe that argument holds water. After all, practicing
> engineers are supposed to keep up with the state of the art. If they
> change the oil recommendations, they don't do it out of sheer caprice.
> Could it be you're confusing the BL bean counters with the engineers?
I don't think it's just me -- I think BL confused bean counters with
engineers <g>.
>
>> And it doesn't matter all that much, I suppose. But if 30wt is just as
>> effective for the purpose, and lasts longer, and is also cheaper, I don't
>> understand the blind insistence on using 20w50.
>
> Additives don't wear out; they become saturated by combustion
> byproducts, etc. In a tranny, they should last for an extended period of
> time. I've never seen anything that said that multi-vis oil becomes
> uni-vis after a period of use. Have you?
Well, yes, as a matter of fact -- that was the source of my statement in the
first place. To be precise, it said "the additive package wears out" -- this
after explaining how viscosity improvers are part of the additive pack.
Unfortunately there was not a specific wearout interval cited, other than a
recommendation to change ENGINE oil at 3000 miles.
> Single-vis oil isn't mnaterially cheaper and is getting hard to find, as is
> non-detergent oil.
True enough :-(
> If detergent oils keep things clean by keeping bad stuff in, why
> not use it?
Not a problem, just remember to change the tranny oil every 3000 miles to
get a fresh load of detergent...
> To answer your question, I use 20W-50 because I live in a climate
> where it gets very hot but not very cold. It seldom gets to 20 F around
> here and my B is garaged anyway but it gets over 100 in the summer.
> When I lived in the high desert, in the winter I used 10W-30 in the
> daily driver '70 B I had then, in both the engine and overdrive tranny.
>
> You're right that it doesn't matter to me 'n thee. But it might cut
> the confusion, for the new LBC owners just coming in, for us to discuss
> it on the forum.
Around here it seldom drops much below 40, and only hits 100 one or two days
a year, so there is some method to my madness <g>. I think the main point is
that almost the entire additive pack of modern motor oil is irrelevant to
the conditions inside the gearbox. Doesn't hurt, but doesn't particularly
help, either. Motor oil is not formulated with the idea it will be used in
gearboxes with a change interval of 10k, 30K or 50K miles, and especially
not in planetary overdrives with cone clutches -- how could it be? The
assumption is that motor oil goes in motors, and that gearboxes use gear
oil. The fact that we get by with all sorts of motor oil formulations (from
non-detergent 30wt in the 50s and 60s through modern SJ rated multigrades)
in the OD basically indicates that the design isn't very fussy.
My logic was that 30wt base stock is still going to be 30wt long after the
additive pack wears out. I'm not so sure about 20w50, and I don't like the
idea of 20w20 in my gearbox. Of course, I change the gearbox oil about as
often as I pull the engine (to be honest, maybe twice in 60K miles) -- this
may not worry some folks on more rigorous schedules.
--
Max Heim
'66 MGB GHN3L76149
If you're near Mountain View, CA,
it's the primer red one with chrome wires
|