Engine oil Recommendation..?

[Bill@Keystone Lake]

1996, 230DA 5.7 Mercruiser with 515 Hours. Boat is used in Oklahoma. Appreciate hearing some opinions...also, does Mercruiser (manufacturer) give a recommendation.

 

[paulswagelock]

The recommendation from 1996 when your boat was built is obsolete. Safe bet, just use the Merc oil, 25w40. You are about to get 100 opinions….. if it was me, Rotella T4 or T5 15w40 every time.

 

[SilentJ20]

Previous owner of my 1994 220BR 5.7 used the 'standard' Mercruiser/quicksilver 25W-40. That's what I just used when I changed for winterizing process. No issues when he ran it, nor when I bought it.

 

[Bill@Keystone Lake]

The recommendation from 1996 when your boat was built is obsolete. Safe bet, just use the Merc oil, 25w40. You are about to get 100 opinions….. if it was me, Rotella T4 or T5 15w40 every time.

I appreciate it.

 

[Bill@Keystone Lake]

Previous owner of my 1994 220BR 5.7 used the 'standard' Mercruiser/quicksilver 25W-40. That's what I just used when I changed for winterizing process. No issues when he ran it, nor when I bought it.

Thanks very much.

 

[Bill@Keystone Lake]

The recommendation from 1996 when your boat was built is obsolete. Safe bet, just use the Merc oil, 25w40. You are about to get 100 opinions….. if it was me, Rotella T4 or T5 15w40 every time.

T4 or T5..? Isn't this for Diesel engines ? Also regarding the 25w40, would this be synthetic or regular...?

 

[Bill@Keystone Lake]

Previous owner of my 1994 220BR 5.7 used the 'standard' Mercruiser/quicksilver 25W-40. That's what I just used when I changed for winterizing process. No issues when he ran it, nor when I bought it.

Synthetic or Regular..?

 

[SilentJ20]

Synthetic or Regular..?

The old bottle of 'spare' oil was regular (from original owner). I have a feeling he used synthetic in his changes recently, as the spare bottle was ancient, haha. But since I've owned it I'm using full synthetic Merc 25W-40. Not very expensive, recommended by Mercury. Good for me!

 

[Fill Ess]

merc 25W40 here

After all it's most recommended

 

[Jbreamsiii]

I went through this on Bobistheoilguy forums and just decided to go with the Mercruiser 25w-40 semi syn because of the corrosion protection factor. It has a decent dose of zinc as well for the my engines cam.

 

[firecadet613]

Rotella T6 15W40. Been using it for multiple 5 7s for years. Oil analysis always comes back perfect...

 

[bfernald0]

Mercury 20w40 Synthetic Blend is what I use. Can't say whether it's better or worse than other products on the market.

 

[paulswagelock]

T4 or T5..? Isn't this for Diesel engines ? Also regarding the 25w40, would this be synthetic or regular...?

It is a diesel rated oil, meaning it has more anti wear additives than a car with a catalytic converter should use, which is why it is perfect for your boat.
25w40 - either their conventional or syn blend is fine.

 

[highslice]

I have used Rotella T6 15w40 since 2016. Used Merc 25w40 semi syn when under warranty, then moved to T5 15w40. I can't say it runs better, but the old oil comes out "cleaner" than when I used the Merc oil. Analysis have all been good. I figure if it is good enough for a hard working 10 year old diesel engine with 600 or 700 thousand miles, it's good enough for a hard working gasser with 550 hours. YMMV.

 

[El Capitan]

 

[BillK2632]

I just can't pass up a good oil discussion!

Any of the aforementioned oils will be just fine. Me personally, I use the Quicksilver oil, non synthetic in my 99 4.3 and if I had your motor I would do the same. If you want to spend more for synthetic or blend that would be fine too. On an average 50hr oil change cycle it really does not matter. Truth is, these are just GM motors and most 10w40 oils will work just fine , but Mercruiser has specific recommendations so it is best to stick to their recommendations. Volvo's for example use the same blocks and they recommend a synthetic 10w40. The main thing is just change the oil at least once a year.

Form the manual for my 1999 4.3 - same would hold true for your 1996 5.7.
Crankcase Oil
To help obtain optimum engine performance and to provide maximum protection, we strongly recommend the use of Quicksilver 4-Cycle 25W-40 Marine Engine Oil. This oil is a special blend of 25-weight and 40-weight oils for marine engines. If not available, a good grade, straight weight, detergent automotive oil of correct viscosity, with an API classification of SH,CF/CF-2, may be used. In those areas where Quicksilver 4-Cycle 25W-40 Marine Engine Oil or a recommended straight weight oil are not available, a multiviscosity 20W-40 (SH, CF/CF-2) or, as a second but less preferable choice, 20W-50, with API service ratings of SH, CF/CF-2 may be used. IMPORTANT: The use of non-detergent oils, multi-viscosity oils (other than Quicksilver 25W-40 or a good quality 20W-40 or 20W-50), synthetic oils, low quality oils or oils that contain solid additives are specifically not recommended. The chart below is a guide to crankcase oil selection. The oil filter should always be changed with oil. 70534

 

[GypsmJim]

First of all, what is the purpose of the question? Trying to find a cheaper alternative? Looking for a better oil?

I doubt anyone ever had an engine last longer because they used Whapadoo Extra Super Doober oil. Besides, how would you know?

Or, You can go to Wally and buy extra super oil at 25 cents a quart. So, how much have you really saved for your gazillion dollar boat?

So, my question is.....if the Manufacture's web site and owner's manual specifies "grade X", why wouldn't you simply buy that and be done with it, without having to stress over what oil to buy?

 

[rustybronco]

I think I'll stick with a good synthetic oil and run it for multiple seasons as long as the fuel system is in decent condition and you don't do only short runs.

 

[Nater Potater]