I don't know the "correct" answer to your question but..... Even with the price difference, I would stick with the marine lube. I have an 89 Evinrude 28sp and it takes less than a quart to fill it up. I'm not sure if there is a composition difference between regular and marine grade gear lube but I don't think it would be worth saving $3 - $5 to find out! Just my opinion.