Is 5w30 the best oil to use in a 4 cylinder 1997 Honda civic, it has slightly over a hundred thousand miles.
about oil on 1997 Honda Civic
5/30 W engine oil is what is called for in your owner's manual. When it comes to engine oil everyone has a preference or anecdotal evidence why one oil is better than another. On engines that have use engine oil pressure to adjust the valves (hydraulic lifters HLA) these engines need an engine oil that has low viscosity ( so oil is circulated around the engine quickly from a cold start up), and also an oil that has good detergency characteristics to keep the lifters clean internally. On engines that have mechanically adjusted valves (your Honda) and have higher mileage and perhaps have started to "burn oil" ,I would have no problems recommending a higher viscosity oil perhaps 10/30.
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5w 30 is recommended for colder areas 10w 30 is recommended for 20 Deg F and above.