I have a 91 Civic base (D15B1) with 129500mi. The engine leaks no oil, does not smoke, and still qualifies as an LEV. I bought the car when it had 112,000 mi on it. The previous owners used Pennzoil 10W30 traditional oil. I started Valvoline MaxLife 5W30 (recommended grade) then. I have heard of new MaxLife Synthetic. I was told not to use traditional synthetic in older engines by everyone I spoke to due to it having the possibility of causing seals to fail. But, synthetic oil overall is better than conventional oils. Would using MaxLife synthetic in my car have negative effects? Since it is a MaxLife product is why I asked. Again, the car has never had synthetic used in it previously.

 

Do a search... there have been MANY topics on this. But I never really found a good answer, people say yes and no.