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Old 06-18-2002, 09:27 PM
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I used to use regular Castrol oil 20w 50 weight in my 1992 300E with 165k miles. I had a slow oil leak from the head gasket and decided to switch to that Valvoline Max Life 20w50 and the leak has slowed down quite a bit to where i don't add half a quart every week. To Synthetic Oil, I sold my 93' Mazda Rx7 last year and used Mobil 1 syn. every 2500 miles. The Buyer insisted i have a rotary engine compression check before he bought it so i did. Rx7 had 122,000 miles and the test came back Excellent. Strong or almost new engines had a rating between 7 to 9 and i had a 7.5. The oil was awesome. But didn't run like it should, Reason- it killed my catalytic converter by clogging it. After talking with a few Mazda techs they said in the Rx7 synthetics don't burn cleanly like dino oil which leaves residues. So i decided not to use Mobil 1 in my 300E. Bottom line, changed oil often in both motors and they haven't let me down, but the difference is I have not had to change the cat on my 300E. I'd stick with Dino!!
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