GT-40 - Oil Recomendations
 

I have the owners manual, but it is at home, and I wanted to pick up some oil on my way home to change tonight.

What weight do y'all use?

If you need to ask that you should probably bring it in for service....

fwiw (which is little) I use SAE-40 in the Tundra.

i have changed oil in many boats. this is a new boat for me, and i want to get the opinion of what people use, especially since this is one of the most popular engines for our sport out there.

my boat is made in america, not japan. tunda oil wont work.

From what I can gather one main concern with the GT-40 regarding oil is zinc content. Our engines are flat tappet and need a certain amount of zinc for protection. I use Rotella 15W-40. Wikipedia lists it as having 1200 ppm. I recommend asking on Planet Nautique and maybe calling Discount Inboard Marine as well. Some dealers/service departments are great but they do not always use the best oil. My old dealer used Napa 40. Please post back your findings.

thanks

I just asked my buddy what he uses on his which is just shy of 1000 hours. He uses Valvoline straight 40 weight changed every 50 hours.

straight 40 weight is tough to find. I've been using Mobil 15W-40 delvac diesel oil in mine since I've got it and have about 450 hours using that oil, no problems so far.

i heard about using diesel oil in boat engines. lots of people do this?

valvoline racing strait 40 weight

Mobil1 15-50. It has the Zinc additives.

valvoline racing has zinc additives as well

Pennzoil Marine 40W in my 2002 SAN.

Rotella t 15 40

+1 for 15W-40. I run this in my gt-40.

I use Mobil1 10W30 in my '02

The Rotella t 15W 40 is a diesel oil...

Rotella 15W-40 here too, although mine is an Indmar / SBC block. I also run Rotella in my 4-stroke motorcycles. It's a great oil, especially for the price.

I was thinking you were speaking of a Ford GT-40. lol, my bad.

ps. It doesn't make a difference WHERE your boat is made, same oil will work just fine. You're not talking about some crazy, super modified race engine with specific, demanding needs.

This is incorrect. Rotella used to be high in zinc and sulphur, two critical components for flat tappet cams. The zinc cushions and protects from metal on metal content, the sulphur enables the zinc to do its job and carries it. Rotella ever since a couple years ago when they changed to the new design on the bottle is low zinc and sulphur.

I used to break in new engines with Rotella, no cam additive. Never had a problem over tens of engines built. Remember breaking in a 302 I picked up some Rotella and thought it was odd that the bottle looked different, but checked and it was the same stuff according to the bottle. Well, on breakin I wiped the cam. That's the first and only cam I've ever wiped. Moral of the story, if you want high zinc/phos avoid Rotella, it isn't the good oil it used to be.

I use Valvoline Racing VR1 for engine breakin. IIRC it's 1300/1200 phos/zinc. Should be fine on it's own but I use cam breaking additive with it. Mobil1 is another good one on Zinc/Phos but only in a couple grades of their oil. It's not well suited to cam or ring breakin though. Amsoil is another goodie, but again only in some grades. I have charts for Amsoil, Mobil1 and Valvoline I'll try to dig up.

Bottom line is in your boat it doesn't matter what oil you use as it's already broken in. Cams don't just go flat, they fail at breakin or fail due to a stuck lifter not rotating, excess valve lash, and various other wear or improper maintenance issue. Personally after breakin with VR1 I use either VR1 or regular Valvoline (depending on engine HP and use) and then switch to Mobil1 after I'm certain the rings are seated and engine is fully broken in.

Bottom line, that engine is well broken in by now, use whatever you want. Personally I would run Valvoline 10w40 with a Purolator PL30001 filter and change it every 50 hours or sooner if it gets dirty.

Great input, Cory.

Filter choice is a huge!!! Avoid Fram & Pennzoil filters. Purolator, Delco, Motorcraft, and Wix are good brands. http://minimopar.knizefamily.net/oilfilters/index.html

I'm not sure we can say "use whatever you want" - marinizers always recommend higher weight oils. 10W40 is the lightest I'd consider.

Its approved for both diesel & gasoline engines.

Valvoline 20w50.VR1. High zinc content which the GT-40 needs.