New Oil

[_X_]

I saw over on Ball of Spray that Rotella is no longer gas engine designated, though CCF has links saying the zinc content is fine for those of us with older boats.

My question is as follows. The guy I bought the boat from a 92 Nautique said he only ever used Mobil1 15w-40 synthetic. I was unable to find that last year when I changed the oil so I went with Rotella dinosaur. Well this week in my search for oil I found this https://mobiloil.com/en/motor-oils/m...vac-1300-super would that work? I honestly can't tell if it is synthetic or not.

Otherwise I can find Mobil1 in a 15w-50 with 1300 for zinc. https://mobiloil.com/en/motor-oils/m...mobil-1#15W-50

I know some guys say no to synthetic in older motors, I just know the guy used it from new in the boat 1993 until I bought it last year. I also noticed before I changed the oil the pressure was a fairly constant 40-50psi while running and with the rotella in I get from 20-60 psi depending on the speed and if I am towing or not,

[a0128]

I run Valvoline 20W-50 VR1 Racing Oil in my 1999 Pro Air. It has the necessary zinc levels for our era engines. I don't think it is necessary to run a synthetic, especially since the oil change intervals are every 50 hours.

[kmarine]

We run 25w40 synthetic blend in all our marine engines and generators. Sierra or Mercruiser or Lucas Farm & Fleet or online is around $20 to $30 per gal.

[2001SAN]

I run Valvoline 20W-50 VR1 Racing Oil in my 1999 Pro Air. It has the necessary zinc levels for our era engines. I don't think it is necessary to run a synthetic, especially since the oil change intervals are every 50 hours.

+1 on the VR1 in my SAN with GT40. Many others also run it in that engine.

D.

[Nautiquehunter]

15 w 50 is the only Mobil 1 weight that Mobil recommends in all marine engines.

[_X_]

Thanks hunter. I doubt the 40 to 50 would matter much and who knows maybe I misheard the guy...excitement level was high buying the first boat.


Sent from my iPhone using Tapatalk

[DW SD]

Believe pcm manual calls for straight 40W in these engines at least for summertime use. Well it does for GT40 which is just the injected version.
Multigrade isn't interchangeable in my view.

Royal purple, amsoil, Brad penn, might be good options. Air cooled Motorcycle oils generally will have more zinc, I think.

Check out Amazon.


Sent from my iPhone using PLT Nautique

[Fgroce]

I know the manual calls for a straight weight oil. But straight weight oils went out many years ago. I would recommend the Amsoil 15w40 Heavy Duty Diesel and Marine oil. It will provide the most protection for your engine.

[DW SD]

Don't want to turn this in to an argument by any means. If you really want to dig deep - you could spend months on bobistheoilguy.com Straight grade motor oils are still readily available, including at walmart.
I think multi-grade standards are often driven by emissions requirements.

I believe shear abilities (protecting metal on metal designed parts) of the straight-grade oils are better, in fact I know of an engine which failed due to an owner switching from 40W to 15W40 thinking it was better. The straight grade's shear properties protects cams and lifters in the non-roller lifter (flat tappet) engines like the GT40.

Not all oil engineering goes towards better protection of engine parts. A big effort is on emissions and fuel economy, even at the expense of protection.

I'm not an oil engineer, nor do I play one on TV

Doug

[Nautiquehunter]

How do you know the 15w50 caused the engine failure?

[DW SD]

How do you know the 15w50 caused the engine failure?

That's what the engine builder told us due to multi-grade use. After the replacement, we've had no issues running 40W. BTW - different engine than GT40. One still that had flat tappet cam. And the failure began at the cams. Thankfully, the previous owner footed the bill, but we were looped in at the time of purchase.

Back to the topic... I have faith, though, in the PCM engineers.

Another benefit of multi-grade, with which I don't have to content is cold-starting. Not sure how many of you run your boat engines in freezing environment. But year round for me, it doesn't get much colder than 50F.

Understand... I'm not looking for a pi$$ing contest, nor am I an oil engineer. I don't know enough to go against the engineers who spec'd the engine oil. Guessing most here don't either.

Good luck!

[nyryan2001]

Indmar released a study a few yrs back... regular motor oil starts to break down in inboard engines right at the 45hr mark.

not all oils are equal in length of protection.... or under extreme conditions like an overheat
or low oil situation