Toyota Repair: Burning Oil, california smog check, wt oil

Question
My 1992 Cressida, a car I dearly love, now has 118,000 miles on it and has recently passed its California smog check.  However, it has slowly become more of an oil burner and is now using a quart of 20-50 wt. oil every 800 miles.  Recently, my mechanic advised me to change the oil weight from 10-40 to 20-50 which I did, believing the increased viscosity would reduce the use of oil.  While I did not closely track the oil use prior to making the switch, I do believe this change reduced consumption to the 800 mile per quart level mentioned above.  My question is "Is there an additive you recommend to further reduce oil consumption?"  I should mention that when the car sits for a day or so, a significant amount of white smoke is seen in the exhaust when the car is first started up.  A greater amount of smoke is noticed after my car has been sitting for say 2 to 3 days but sitting for a week or so shows no greater smoke output.  Any ideas you have would be appreciated. John

Answer
I don't recommend additives because they don't work.
The oil consumption at 1qt per 800 miles is not that bad even for 118,000 miles, the factory considers 1qt per 1000 miles normal consumption. I'm not sure that you have a problem with oil consumption but I do think that there is another problem based on the fact that there is some white smoke(steam) coming from the tailpipe which indicates a headgasket problem or an internal combustion leak, ask your mechanic to do a block test to check for a blown headgasket, an oil burning condition will emit blue smoke from the tailpipe, not white.