Best oil for a Mercruiser 3.0L?

[81 Checkmate]

Agree Bruce.....Chevy wouldn't have done such a thing without extensive testing...... At $7.50 a quart it better be a quality oil.....By the way the SS has the LS-2 motor.

 

[HT32BSX115]

The Chevy Corvette comes from the factory with Mobil 1 5w-30. I would think if GM thought it was a problem, they wouldn't be using it.

AND, in addition, ANY "X"W-30 synthetic oil will always behave like, and essentially IS a straight 30W oil at 100C

 

[friendly_jacek]

AND, in addition, ANY "X"W-30 synthetic oil will always behave like, and essentially IS a straight 30W oil at 100C

If you're such a self-declared expert on the subject, how come you haven't heard about viscosity shear?

 

[fishrdan]

If you're such a self-declared expert on the subject, how come you haven't heard about viscosity shear?

Keep it friendly!................ (no personal attacks, forum rules)

 

[Fastatv]

Oil questions......well, all I can say is that I use Rotella 15W40, and an AC/Delco oil filter. But as said by many, if you use the correct viscosity, or close to it, you should be good to go.

 

[Lou C]

Well well it never ends....
You can use anything you want...but as a general rule....I'd advise staying away from lower vis multi weights...like 5/30, 10/40. You need a heavier oil that will not shear down when the engine is run at 3500-4500 rpm for hrs at a time which is how boat engines are used. So, you can use:
straight 30, 40, 20/50 or merc's 25/40. I would not use a 10w-anything in a marine inboard. It will shear down over time. The multi-vis function of motor oils comes at a price. The price is shear stability in very heavy duty use. Modern vehicles have at least a 5 speed transmission that allows the engine to relax at highway speeds. Boats have 1 speed no relaxing.
I use the Merc 25/40 in my old '88 4.3 original engine never rebuilt. Even after running on plane, it still holds 25 psi at slow idle. After it idles and cools off a bit the idle oil pressure is 40 psi. I don't think I'd get that with a lower vis oil.....

 

[HT32BSX115]

If you're such a self-declared expert on the subject, how come you haven't heard about viscosity shear?

Wow! Aren't we touchy!

No. I haven't declared myself to be an expert on anything............BUT, I can read.
(Oh....wait a min..........YOU think someones "avatar" makes them an expert on "stuff"........... My dad (rest his soul) actually worked for Associated Oil Company (the original Flying A......... I just happen to LIKE the picture!!)


But, if you choose to read too, you can read the specs on just about any oil and read what the manufacturer claims the viscosity actually IS according to ASTM standard D-5293 (for cold cranking to test for apparent viscosity) and maybe D-4741 (for the kinematic viscosities at 100 and 150 degrees C.) Oh, by the way, those oils MUST be tested and pass all those tests to be CERTIFIED by the SAE. (Some oils by the way are not "certified" .....Some Am$oils come to mind as not being certified.......)

Then knowing that NON-syn oils (like 10W-40 for example) are actually an SAE 10W oil with viscosity improvers that, (Yes Virginia, if you run it long enough) will actually "become" a 10W and and maybe 'shear' lower eventually..............

BUT, synthetic multi grades do not use visc-improvers like non-syn oils and stay in grade MUCH longer especially the higher grade at higher temps.............AND they behave "like" single grade oils (at the higher "number")

But you don't have to be an Electrical Engineer to know this, you just have to do a little reading of ASTM standard test methods and results.......... Maybe I have WAY too much time on my hands and I like to do some reading....and pass it on............. But it STILL doesn't make me an expert on anything............I'll leave that to the people that "test" "snake-oils" and additives and report on forums that they "have never had a problem" with them.............

Well well it never ends....
You can use anything you want...but as a general rule....I'd advise staying away from lower vis multi weights...like 5/30, 10/40. You need a heavier oil that will not shear down when the engine is run at 3500-4500 rpm for hrs at a time which is how boat engines are used. So, you can use:
straight 30, 40, 20/50 or merc's 25/40. I would not use a 10w-anything in a marine inboard. It will shear down over time. The multi-vis function of motor oils comes at a price. The price is shear stability in very heavy duty use.

And of course, as always, Lou C is SPOT-ON..........which is probably why Mercruiser, OMC and maybe Volvo has always suggested against Multi-visc (NON-syn) oils. They don't seem to suggest against the syns.......


Cheers,


Rick

 

[Fastatv]

I think I have kind of said that oil is oil but.....I will retract that statement....to a degree and here is why. I bought a rough old Larson 170, with a 3.0L engine. The oil in the engine looked good, but I changed it anyway, with 10W30, really for flushing out purposes. I ran it a few short trips, cold engine, 40 PSI pressure at idle, warm engine at idle, about 20 PSI. When running about 3000 rpm, warm engine PSI, 40. Now, after changing to Rotella 15W40, engine oil PSI is at 60, cold idle, and almost 40 PSI at warm idle. Now at 3000 rpms, a steady 50 PSI, warm engine. I am very pleased, and next oil change, going to use the 25W40 as recommended. I think I must have let myself get caught up in the "thinner viscosity", better mileage thing as one might with automobiles.

 

[liusigou]

How much engine oil and How much gear oil should be pushed for mercruier 3.0 L motor?

 

[Bondo]

How much engine oil and How much gear oil should be pushed for mercruier 3.0 L motor?

Ayuh,..... 5 qts. 'n 1.5 qts,....