jim beam wrote:
> Leftie wrote:
>> Elle wrote:
>>> On Sep 11, 8:41 pm, jim beam <m...@privacy.net> wrote:
>>>> here's something to consider - an old "trick of the trade" is to use
>>>> some of that crappy "stop oil consumption" additive when a dealer sells
>>>> a known dud car. it works fine for a while, then, once a few months
>>>> have gone by and it's no longer a quick come-back, it breaks down and
>>>> oil consumption rises again.
>>>
>>> I was not aware that such additives existed but I can certainly
>>> believe this is what happened and I got sold a car with a way worn
>>> engine. This may be a lesson of used car buying, even with a clean
>>> title and second owner status. Worst case I guess I may live with the
>>> oil consumption and then at some point chase down an engine to swap
>>> in.
>>>
>>> I will keep this thread updated.
>>
>>
>> There are two types of additives to lower oil consumption. One
>> swells the valve seals; if you did the seal replacement right then
>> you can rule that out. The other kind thickens the oil to slow blow-by
>> past the rings. That would have been removed not long after the oil
>> change. You can do a simple test to see if it's worn rings: pull all
>> the plugs and the air filter, then run a compression test with the
>> throttle wide open. If you have worn rings OR valves, the compression
>> will be low. Then squirt about a tablespoon of higher-weight oil like
>> SAE 80 or 90 into each cylinder and repeat the test. If the
>> compression shoots up, you have worn rings. It if only rises slightly
>> or not at all it's worn valves.
>
> valves don't affect oil consumption.


Valve seals do, however. I was assuming that worn valves would be
leaky as well, but maybe not.