93 SW2 consuming oil

I know early Saturns use oil. Mine goes through a quart every 500 miles.
But it happens strangely. I check it every few days, and it drops slowly
for 3 or 400 miles, then suddenly goes to below a quart low. There is no
visible smoke out the exhaust, and I put dye in the oil and there were no
major leaks anywhere. My mechanic suggested I switch from Mobile 1
synthetic to a 10-40 regular oil (he said synthetics get consumed
faster).

Any ideas why I am losing oil, and what to do (by the way, my 1999 SW2
doesn't use ANY oil).

Thanks for any help you can give me

Lee

 

By the way, I recently put in a new PCV valve, then replace it with an
original equipment Saturn valve.

 

Are your oil pan bolts tight? I ask because sometimes they loosen up
with age, and can lead to oil loss that might not be readily apparent
(at least not in your driveway).

Dave

 

IIRC about the oil level not appearing to be evenly representational of the
actual levels, it was something to do with the area the dipstick reads being
funnel shaped. I think Kirk used to be up on this topic - maybe he will
chime in. For example if you see the stick at about half-way, it seemed to
take more than a half-quart to return it to full.

My 97 was much better at using less oil after the rebuild (new rings, cyls
honed and new valve stem seals) and I could still cause the level to drop
depending on how 'Spirited' I drove it. My usage also went up when I
switched to synth and I went back to dino oil but changed it like every 2000
miles.