4 Stroke Engine Oil – Outboard Question

I have a 2008 Yamaha F90 that I do oil changes on myself. I have been using standard Yamalube 10W30 per dealer recommendation and do it 2x per year based on my usage (estimating close to 150hrs of run time per year). I am looking at switching to a synthetic blend or full synthetic oil going forward. The oil is pricey at the dealer so I am looking for alternative sources. The reason I am looking to get away from a standard 10W40 is that is looks very dark/used when I drain it (no burnt smell or anything like that) and I’m thinking that a synthetic blend or full synthetic may hold up better

My local Farm & Fleet has Quicksilver Synthetic Blend but only 25W40. Has anyone used this or would something like Mobil1 Synthetic 10W40 work just fine? When I used to have a motorcycle (sport bike), it was recommended to use a full synthetic, but I’m not sure about outboards. I’m just not sure if the NMMA certification means much since there are limited companies that show that on their product

Thanks

http://www.amsoil.com/shop/by-product/motor-oil/marine/10w-40-synthetic-formula-4-stroke-marine-oil/?code=WCFQT-EA

I use Amsoil 10-30 marine in my F150. No issues.

You are changing so frequently that you could get away with using HD auto synthetic. Oil with same viscosity is only different in the additives. Look at a synthetic for diesels. It will be much cheaper than marine and easily hold up to 75 hours of water time.

The big thing for an outboard is to make sure it’s an FC-W rated oil. Automotive oils are designed to run at a higher temp so if they are ran in an outboard that runs much cooler they tend to build more moisture. There are a lot of manufacturers that now have FC-W rated oils, and several of them are synthetic so there are options out there.

Thanks for the info everyone

Been using Mobil 1 for years – no problems.

-J.

Mobil 1 here as well, about $24 for 5 quarts at walmart. Great oil at a good price.

Mobil 1 for me too for 6 years now.