I know this has been discussed before, but I'd like a clear choice:My summer daytime temps are never below 80 and often in the 90's; I don't have to worry about cold starts in winter. For best engine longevity in the summer(not worried about slight improvement in milafe or power) which is BEST for my 67 300hp with moderate to high milage-10w30 CJ-4 or 15w40 CJ-4?I can get either one. Will the 10w30 which is recommended in the 1967 owners' manual be too thin during these hot summers?
Thanks
Thanks
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