Other than the 1993 E 300, I have a87 toyota MR2 ttop, nice little car I picked up for 1000 from a friend two years ago. It was using a lot of oil, a quart every 300 to 500 miles.
Finally decided to add a pint if ATF to the cranckcase and now it uses a quart every 1500 miles. Not necesary what I recommend but it worked like marvels mystery snake oil.
I'll try to go back to only 10-40 now that I will change the oil and filter. see whathappens.

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Thanks, Juan