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Merc 25w40

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lilguy

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Any reason to try something different? The discussion can go on forever, first 2 boat used straight 30 or 40 wt. Merc oil on this boat. Thanks all
 
Depends if you're engine is emission controlled with a catalysts system?

What type of engine & year are you running?
 
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07 5.0 MPI, no cat. First boat was OMC 5.7 and they told me 30 wt back in 89. Second boat Merc 6.2 and was told 40 wt. Don't use it alot so want an oil that also protects in long lay ups.Thanks
 
lilguy said:
07 5.0 MPI, no cat.
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Then the manufacturers recommended oil specific specification is not as critical for you're engine vs the newer catalysts system.

If you decide to not run the manufacturers recommended engine oil brand & weight, then you are in the clear to run just about any good quality name brand oil & weight you choose that is on the shelf.

Try to pick your oil weight to average the ambient air temp you would run in if possible.

My personal recommendation would be to pick one and stick with it.

Here's a hint, new engines from GM are said to come with straight 30 weight oil.

If Mercury MerCruiser Full‑Synthetic, 20W‑40 oil is unavailable, use the following lubricants, listed in order of recommendation. If you are servicing a catalyst engine, use these for short periods of time only.
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, straight‑weight detergent automotive oil according to the last row of the operating chart below.​
NOTE: We do not recommend non‑detergent oils, multi‑viscosity oils (other than as specified), non FC‑W–rated synthetic oils, low‑quality oils, or oils that contain solid additives.
SAE 30 W, (32° F) - (50° F)
SAE 40 W, (50° + F)

In the end, armed with this information above, it is your choice.;)

Hope this help, good luck.:)​
 
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