Merc 5.7 i/o oil viscosity

[keperman]

1994 5.7 Mercruiser Alpha 1 gen II, Wellcraft Eclipse 210 SC.

Boat is used for cruising/skiing/fishing from March through October in N. Tx. where air temps range from 50 degrees to 110 degrees.

should i use 10w-40? any need to use synthetic if i change it every season?

thanks

 

[dubs283]

Re: Merc 5.7 i/o oil viscosity

25W-40 is mercruisers top recommendation for sterndrive engine oil

SAE 30 is second

 

[Howard Sterndrive]

Re: Merc 5.7 i/o oil viscosity

should i use 10w-40?

no - Mercruiser recommends nothing that starts with any number lower than 20

any need to use synthetic if i change it every season?

no need
personal choice- using synthetics does not change Mercruiser's recommended change interval anyhow
http://www.mercurymarine.com/servic...ntenance/faqs/mercruiser/?category=fuel#MCOil

 

[betayv]

Re: Merc 5.7 i/o oil viscosity

I will use 10w40, hey you have a pic of the boat I have a 1994 eclipse...

 

[fossill]

Re: Merc 5.7 i/o oil viscosity

I'd be curious to know what Merc recommends for their engines with cat converters as the only compliant oils for those engines in the GM automotive world is 5W-30 or 10W-30 grade stamped "energy conserving".
In any case 10W-40 in your engine will work perfectly.

 

[Gary H NC]

Re: Merc 5.7 i/o oil viscosity

Merc does not advise using any 10 weight oil...
You would be much better off using straight 30 or 40 weight if you do not want to use the 25w-40 Merc oil.

Read the service bulletin Don posted...

 

[Howard Sterndrive]

Re: Merc 5.7 i/o oil viscosity

In any case 10W-40 in your engine will work perfectly.

if by "work perfectly", you mean run with low oil pressure and damage the bearings.

engine would not do well with 10W40 in Texas @110F ambient

 

[keperman]

Re: Merc 5.7 i/o oil viscosity

i have one but do not know how to attach it to a reply. I need to get some more pictures. Maybe this weekend. Season almost over here.

you have any pics? I have the Smurf Blue interior ;-)

 

[keperman]

Re: Merc 5.7 i/o oil viscosity

i have one but do not know how to attach it to a reply. I need to get some more pictures. Maybe this weekend. Season almost over here.

you have any pics? I have the Smurf Blue interior ;-)
Attached Thumbnails

 

[fossill]

Re: Merc 5.7 i/o oil viscosity

if by "work perfectly", you mean run with low oil pressure and damage the bearings.

engine would not do well with 10W40 in Texas @110F ambient

It's still a 40 weight oil just like the Merc 25W-40 stuff when its hot. The 10W only applies when the oil is cold. The only viscosity difference between the two is that the 10W40 will flow better on initial start up.

 

[Don S]

Re: Merc 5.7 i/o oil viscosity

It's still a 40 weight oil just like the Merc 25W-40 stuff when its hot. The 10W only applies when the oil is cold. The only viscosity difference between the two is that the 10W40 will flow better on initial start up.

Please explain the part highlighted in yellow below, and why Merc says any other multi grade oil but 25W40 should not be used.

 

[fossill]

Re: Merc 5.7 i/o oil viscosity

Hey I hear yah, I'm just saying that a 10W-40 is the same viscosity as a 25W-40 and a straight grade 40 when its hot.
Merc says only 25W40 for multigrade. Volvo says only 20W-20, 15W50, 20W-50 for multigrade in their engines. If you can run those grades in Volvo, why not a Merc and vice-versa? Both are just rebranded GM engines.

http://www.gm.com/vehicles/innovati...engines/specialized/marine/marine_engines.jsp

 

[rodbolt]

Re: Merc 5.7 i/o oil viscosity

and item number 3 in the above.
a NMMA FC-W rated oil.
yama-lube 4M is FC-W rated and can be had in 10w-30,10w-40 and 20w-40.
FC-W is four cylce water cooled, its designed with some other additives to aid in corrosion protection and the marine engine duty cycle.
some years back merc specifically stated DO NOT use synthetic, that same 5.7 painted red had an owners manual that stated ONLY use synthetic.
the world gets funny with oil sometimes.

 

[dan t.]

Re: Merc 5.7 i/o oil viscosity

Mobil-1 15w50

 

[jason32038]

Re: Merc 5.7 i/o oil viscosity

10w 30 sounds good for the temp range.

 

[Howard Sterndrive]

Re: Merc 5.7 i/o oil viscosity

10w 30 sounds good for the temp range in Greenland.

^^fixed

 

[Lou C]

Re: Merc 5.7 i/o oil viscosity

One point that is getting missed is that multi vis oils, esp non synthetic are not magic, yes they are able to span that range when they come out of the bottle but they need viscosity index improvers to do it. When they start to break down, the viscosity breaks down, its not uncommon for a 10W-30 conventional oil to shear down to a 20 wt when in use for a while, whereas that would be less likely with a straight weight conventional or a syn multi vis which does not need viscosity improvers. Car engines do not see the sustained high revs that boat engines see so that viscosity breakdown is more of an issue. Merc says that the 25/40 is not a conventional multi vis (does not use viscosity index improvers) but a combination of oil of those 2 viscosities, presumably to give better low temp performance than a straight 40 would. If you are not boating under 50 *F just use straight 40, simple, you can use Chevron Delo 400, Shell Rotella T or Pennzoil Marine straight weight...why experiment, the sterndrive companies have done the experiments for you already...

 

[Fishermark]

Re: Merc 5.7 i/o oil viscosity

Sit back and let the games begin!

 

[Aloysius]

Re: Merc 5.7 i/o oil viscosity

Ford uses 5-20 for its engines. The bearings are not a problem. The ONLY oil related issue I've ever seen is piston scuffing at 260 degrees with very light redline oil.

GM builds those engines. If GM recommends 10-30, then who cares WHAT Mercury says............

 

[Alpheus]

Re: Merc 5.7 i/o oil viscosity

Not that this matters to the OP, but I would think its because GM is not the ones who are paying for warranty claims.

If my engine was under warranty and Mercruiser says to run panther pi$$ in the engine. Guess what. Ill be at the zoo in the big cat section with a plastic cup...