Mercruiser 7.4L engine oil question

[Baby Blue]

What do you use for engine oil in your 454? Mercruiser recommends quicksilver 25w40. I was told by a mechanic to run synthetic. just curious any thoughts from the board here.
thanks, BB

[mmwjr]

Like all engines it is typically recommended to use the manufacturers recommended oil.
I use the 25w 40.
Switching to a synthetic is not recommended after high hours have been accumulated.

In summary with the average use per season being about 50 to 100 hours I would just use the quicksilver

[biggerseagar]

What Mike said BB.

My walmart even sells the quicksilver 25w40 brand....... yours might too.

Roger

[jontyelpes]

Mercury Marine specifies that the following lubricants may be substituted for short-term use. They are, in order of the company's preference:

1. Mercury Quicksilver 25W-40 Synthetic Blend NMMA FC-W rated 4-cycle MerCruiser Oil.

2. Mercury Quicksilver 25W-40 NMMA FC-W rated 4-cycle MerCruiser Oil.

3. Other recognized brands of NMMA FC-W rated 4-cycle oils.

4. A good grade of straight-weight detergent automotive oils.

[shrew]

They used to make a Mercruiser brand of oil for outdrives as well as a Mercury brand for outboards. I think it all comes out under Mercury now. Quicksilver is owned by the same company, so I never understood why they had so many brands. I'll either Mercruiser or Mercury 25-40 provided it is for Sterndrives/Inboards. I try to get Synthetic, sometimes I have to go with a synthetic blend. However my engine came from the factor with synthetic. (496/8.1). As stated by MMWJR, if the engine has been run with stanard all its life, then I would not put a drop of synthetic in there.