Pondering going synthetic oil (5-50)

[heinz wittenbecher]

It's oil change time again and am pondering should I or shouldn't I.

I have about 100k on the engine and it uses about 1 litre at 5-600 miles.
It's been like that pretty well from day one.

Oil pressure sits about 25lbs at cruise temp(55-60mph).

I think I have all leaks under control .

I'd like to get a few more miles (or at least another season) out of the
engine and have been listening to 2 sides of pros and cons, or rather do and
don't, i.e. I've not been able to get enough info to decide for myself.

I'm wondering what to expect. Increased oil consumption? I have been told
that the switch to synthetic will have an initial cleansing affect and
require the filter to be changed in between. Compression has been steady
between 134-138. Perhaps not the greatest, but it still has lots of poop. Is
it going to get too clean? On the other hand, if it's that close I'd just as
soon know it

Hopefully there are some actual experiences out there that at one time or
other were in a similar circumstance.
Perhaps I should just leave well enough alone and concentrate on next
engine, but this one runs rather nice yet so I'd hate to throw it away.

Heinz
'76 Transmode

 

[william d. minor]

Heinz,

I used to get 500-600 miles to the quart also, but then I switched to
Castrol Syntec 5-50. I now get 1500+ to a quart, no smoke at startup,
easier cranking, and slightly better mileage than before. My coach has
168,000 miles on it, the last 30,000 on synthetic. I am a true believer
in the synthetic route as it helps under extreme temperatures, and our
beloved GMC's have many extreme temperatures (mostly HIGH).

Bill

 

[heinz wittenbecher]

That's good news. Thanks Bill.

Seems like you switched under similar circumstances. Been just reviewing the
latest compression tests (120/125 cold, throttle closed, 150ish throttle
open)

Thanks again

>
> Heinz,
>
> I used to get 500-600 miles to the quart also, but then I switched to
> Castrol Syntec 5-50. I now get 1500+ to a quart, no smoke at startup,
> easier cranking, and slightly better mileage than before. My
> coach has
> 168,000 miles on it, the last 30,000 on synthetic. I am a
> true believer
> in the synthetic route as it helps under extreme temperatures, and our
> beloved GMC's have many extreme temperatures (mostly HIGH).
>
> Bill
>