Engine Oil Recommendation

[Skip ThunderBolt]

Hello Everyone,
I am ready to do my first oil change on a pair of HUGE Merc 454 V-8s in my 1989 Sea Ray 390. The engines have 1259 hours and run great. Any advice on the best engine oil to use on these behemoths? Thanks as always for the advice.

Mack

 

[mrsrobinson]

Mack, there are a lot of good threads here on this subject. Most from what I have read say go with what the manufacturer recommends. I used Quicksilver 25-40 in my big blocks

 

[Golfman25]

I’d go with the merc quicksilver 25-40 as well.

 

[paulswagelock]

The Merc branded 25w40 would be fine. If it were me with those motors, Rotella T5 or T4 15w40 would be in the sump.

 

[HardHead]

Hello Everyone,
I am ready to do my first oil change on a pair of HUGE Merc 454 V-8s in my 1989 Sea Ray 390. The engines have 1259 hours and run great. Any advice on the best engine oil to use on these behemoths? Thanks as always for the advice.

Mack

In my 96 370DA I have used straight diesel Rotella 40W for the last 10 years. The previous owner also used straight 40W. It works as long as you only boat in warmer temps 55+.

 

[mrsrobinson]

That was going to be my other suggestion; find out what the PO used, and use that.

 

[Skip ThunderBolt]

Thanks, everyone. I just ordered Merc 25W-40 from Amazon. Any advice on filters?

 

[JayhawkCurtis]

I have a oil question, on my last boat with a 3.0 merc, I used quick silver 25-40 because that is what the previous owner used, on my current 350 mag, I use merc brand 25-40 because that is what the previous owner used. I still have several quarts of the guick silver, can you mix these 2? I was told they were the exact same oil just different packaging. anyone know for sure?

 

[Yendor]

That difference (IF there is any) would not keep me from using what I had on hand.
Most likely there is NO difference, anyway.

I've mixed oils more dissimilar than that and never had any deleterious effects.


@Skip ThunderBolt - My preference is WIX which is also who makes NAPA Gold series
Anymore, I stay away from FRAM.

 

[mrsrobinson]

Thanks, everyone. I just ordered Merc 25W-40 from Amazon. Any advice on filters?

I got mine from Napa, Gold.

 

[Scott215]

I would have to say the 25 40semi synthetic Merc

 

[Golfman25]

Thanks, everyone. I just ordered Merc 25W-40 from Amazon. Any advice on filters?

The quicksilver or merc specked for the engine. Or Napa gold.

 

[wineknot]

Thanks, everyone. I just ordered Merc 25W-40 from Amazon. Any advice on filters?

@Skip ThunderBolt - If you want to see the filters that Mercury Mercruiser recommends for that engine then go to their parts lookup website. You can find all the illustrated parts drawings for your specific engine (and sterndrives also) by just entering a serial number: https://www.mercurymarine.com/en/us/parts-and-accessories/parts-catalog

 

[Scott215]

Quicksilver and Sierra are both good

 

[northern]

1989 twin 454 380 Aft Cabin. Manual says 30 or 40 oil. We have 3600 hours on the engines use 40 oil at first used Delco then switch to shell at 1500 hours. Engines with Shell Rotela do not use oil and there is no blue smoke. We got boat at 650 hours pervious owner used 15 40 Delco. Change oil every 100 hours. Have gone to 130 hours a few times. Change oil in transmissions every second oil change. Grease shaft bearing support near transmission every oil change

 

[Stee6043]

1989 twin 454 380 Aft Cabin. Manual says 30 or 40 oil. We have 3600 hours on the engines use 40 oil at first used Delco then switch to shell at 1500 hours. Engines with Shell Rotela do not use oil and there is no blue smoke. We got boat at 650 hours pervious owner used 15 40 Delco. Change oil every 100 hours. Have gone to 130 hours a few times. Change oil in transmissions every second oil change. Grease shaft bearing support near transmission every oil change

3600 hours!!!! But the internets would suggest all gas engines implode at 1,000 hours!

 

[Scott215]

That's a lot of hours. You are lucky to keep the great maintenance schedule

 

[Soulshine]

Straight 30 in mine of similar vintage.

PITA finding 14 quarts on the shelf though.

What does your manual say?

 

[Tri County Trail]

The Merc branded 25w40 would be fine. If it were me with those motors, Rotella T5 or T4 15w40 would be in the sump.

Any reason NOT to use T6 full sync or Mobil 1 Advanced Full Synthetic Motor Oil 15W-50 , Im changing over from mercriser 25-40.

 

[paulswagelock]

Any reason NOT to use T6 full sync or Mobil 1 Advanced Full Synthetic Motor Oil 15W-50 , Im changing over from mercriser 25-40.

Mobil 15w50 is not a bad choice, but it sheers easily so I tend to shy away from it a bit in marine applications. T6 15w40 is a good oil, but there is no real advantage in a marine application for full synthetic since we generally are not looking for extended change intervals or cold weather starts. I have not seen the UOA’s in the past year, but T5 had a slightly better add pack regarding old school anti-wear additives. All of these are decent choices as is the Merc OEM oil.