1200 MPG and 2500 MPG, not good

[Walsted]

My Miata has reached the point where it gets about 1200 miles per gallon of motor oil. Given that the car hasn't been a garage queen, (412K miles,) and I get a cloud of blue smoke after sitting overnight, my guess is that the valve stem seals are probably shot. Additionally, on somewhat random occassions, coolant disappears. I check daily, and when it disappears, it is about a pint that is gone, sometimes up to a quart, and I check at least every other day, which could be every 160 to 300 miles. This could be from an unfound small leak, but the randomness suggests to me that it may be a head gasket issue or something similar, and if it is a head gasket issue, that could be where the oil is going as well.

My current train of thought is that I should do compression checks when I do plugs, soon, and if numbers are good, assume valve stem seals and a small, as yet undetected, coolant leak. If numbers are bad, assume head gasket and/or head and/or block warpage. Does anyone have experience in these areas, and if so, do you have any suggestions?

Thanks,

[MC70]

412K on the engine? That is quite long lived for any Miata engine. My advice? Stop by TDR and give them $400 for a much fresher one.

[OZMDD]

If they have complete running motors for $400, I'll take 3!

[Rogue]

Yeah those are the 99/00 BPs though.

[Walsted]

I really don't think I can get a decent used engine for even close to $400. Car-part.com was showing a LOT more than that,with a lowest non-core listing of $900.

Thanks,