What oil should I use?

[Lou C]

I switched from Dino oil to syn blend, no leaks before and no leaks after…this is on my 1988 4.3, the short block is original…

 

[dingbat]

No reason whatsoever to use synthetic oil in a water cooled motor that goes 25-30 hours between oil changes.

 

[Scott06]

Poppycock. I switched, from Dino Oil to Synthetic on an Engine with 110,000 miles on it, and it didn't leak, or burn it any faster. It now has over 250,000 miles on it and still No Difference.

Agreed I switched several cars over from dino to synthetic over the years no issue, including my boat. After repower the warranty required dino oil for first 100 hrs.

We are turnign this into another bottomless pit oil thread. The biggest issue OP should concern himself with is he has a flat tappet cam most modern oils dont have the same amount of zinc as oils used to. Use rotella T4 for this reason and dont over think it

 

[JASinIL2006]

Dino oil is fine. Synthetic oil is fine. Just make sure the oil has sufficient zinc and is of the proper viscosity and all will be fine. Synth oil will not cause your seals to leak, etc.

 

[Lou C]

One of the highest in zinc oils is Valvoline 20/50. 1400 ppm.

 

[Scott Danforth]

I miss the old popcorn and oil thread emojis

 

[jimmbo]

GM used to, maybe still does, market an Oil Supplement, aptly called Engine Oil Supplement(EOS) which they recommended during Break In. I recall the printing on the Can, saying it was good for Cam Break In. It was a delightful Chemical Stew, that while Thicker than Oil, it was runny compared to the Oil Honeys that did nothing.

 

[racerone]

Use the Mercruiser 25 / 40 oil.-----Sterndrives operate in a tough environment.-----Big waves are tough on bearings.

 

[Lou C]

The conventional Merc 25/40 has about 940 ppm of zinc, the syn blend 25/50 has 1240 from my oil analyses
Like I said a cheaper option is Valvoline VR-1 20/50 that has 1400 ppm of zinc.
On my engine it doesn't matter that much because it has a roller cam.

 

[Scott Danforth]

Rotella T4 14W40 is 1200ppm

 

[matt167]

GM EOS has been gone for some time now.. there is a product that does the same thing available from parts stores in a yellow bottle

 

[Franco_boater]

is it worth to stitch to Valvoline 20w50 instead of 25w40? In the manual it’s not recommended at all…

 

[jimmbo]

You really can't Go Wrong, by following the Manual.

 

[Bondo]

is it worth to stitch to Valvoline 20w50 instead of 25w40? In the manual it’s not recommended at all…

Ayuh,........ Sure, if it makes you feel better,......
'bout any clean fresh motor oil, won't hurt a thing,....

 

[Scott06]

is it worth to stitch to Valvoline 20w50 instead of 25w40? In the manual it’s not recommended at all…

I have run Mobil 1. 15w-50 for years it’s seems to keep the oil pressure high on longer sustained high rpm runs Than rotella 15-40 or the merc 25w 50

in my opinion depends on how you use your boat. I tow watersports with a heavy load in the boat daily, spend a lot of time above 4 k rpm.

 

[Scott Danforth]

Tractor supply has Rotella T4 15W-40 for $39 for a 2.5 gallon jug. the T5 and T6 is $59. since the boat takes 2.25 gallons...... you can tell which oil I buy for the boat/lawn mower/step sons car.

 

[Scott06]

I have run Mobil 1. 15w-50 for years it’s seems to keep the oil pressure high on longer sustained high rpm runs Than rotella 15-40 or the merc 25w 50

in my opinion depends on how you use your boat. I tow watersports with a heavy load in the boat daily, spend a lot of time above 4 k rpm.

I meant than merc 25w -40. merc does make a 25w-50 that works great too (I think for the verado?) , its just expensive compared to getting mobil from wally world

 

[Scott Danforth]

Merc buys oil and private brands it. Its citgo oil..... good ole Hugo Chavez and Nicolás Maduro

 

[jimmbo]

Merc buys oil and private brands it. Its citgo oil..... good ole Hugo Chavez and Nicolás Maduro

It is Blended to a Spec that Mercury specifies