16:1 for sure. Ignore all the hype about “today’s oils being so much better, you need less” on this engine. This engine has “plain bronze” rod bearings that require alot of lubrication. If the rods don’t get the lube they crave, you will end up pitching a rod probably through the side of the block. The great thing about these engines is when they are in good tune, they hardly smoke at all, even at 16:1
