Merc oil vs Mobil 1

Merc4ever

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In a GM Mercruiser what are the thoughts on using Mobil 1 over the synthetic Mercury oil? Is it really necessary to drive 3 hours to find 5 quarts of Merc juice when I can get Mobil 1 a lot easier? If so what weight is recommended and is Merc oil really better for my engine?
 

sea wolf

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Re: Merc oil vs Mobil 1

I don't believe that Merc owns it's own oil refinery. They just buy the oil from whoever & put a Merc label on it. It's called marketing. So, go with the Mobil. I'm not sure on the weight as you didn't post what setup you have. But, probably straight 30.
 

Merc4ever

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Re: Merc oil vs Mobil 1

I don't know if they make a straight 30w in synthetic. I was thinking more in line with the 15-50w high revving racing oil.
 

fossill

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Re: Merc oil vs Mobil 1

Merc sells SAE 25W-40. Volvo Penta sells SAE 30. Both are the same GM engines. GM said to use 5W-30 back then when it was in their vehicles.
Personally I think the engine will rust away long before it fails because of what oil your using. Use whatever you want. My humble opinion.
 

JustJason

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Re: Merc oil vs Mobil 1

15-50w high revving racing oil.

50W oil is a bit thick for engine oil, especially if you live outside of florida or texas, and especially for an engine that rev's relatively low.

I used to own Triumph TT that called for Triumph Racing 4T 15W-50 racing oil at 12 bucks a quart... It was nothing more than mobile with a blue triumph logo on it. But that engine redlined at 16.5K RPMS (yes you read that right) and lived most of it's live at 8K and above.
I also used to own a heavily modified ford taurus SHO with a yamaha V6 engine. That sucker would pull through 13K, I also ran 15-50 in that.
Your boat engine rev's on average 4500 RPMS peak... you'll be fine with a 30 or 40 weight base stock oil.
 

ken_23434

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Re: Merc oil vs Mobil 1

50W oil is a bit thick for engine oil, especially if you live outside of florida or texas, and especially for an engine that rev's relatively low.

I used to own Triumph TT that called for Triumph Racing 4T 15W-50 racing oil at 12 bucks a quart... It was nothing more than mobile with a blue triumph logo on it. But that engine redlined at 16.5K RPMS (yes you read that right) and lived most of it's live at 8K and above.
I also used to own a heavily modified ford taurus SHO with a yamaha V6 engine. That sucker would pull through 13K, I also ran 15-50 in that.
Your boat engine rev's on average 4500 RPMS peak... you'll be fine with a 30 or 40 weight base stock oil.

I had a 2001 TT also. I always used the Mobil 1 Racing 4 (no T) from Autozone. I now have the 2006 Daytona 675. It calls for the same oil and now the Mobil 1 at Autozone says "4T". Not really sure what changed in it. It's still about $10/quart though.

I have always wondered why the recommended oil for a given engine (made by GM) will have a different oil recommendation based on what drive is mounted BEHIND the engine. Heck, I think the oil cap on my engine even says 5w-30 even though the manual for the engine (Mercruiser) says 25w-40.
 

Simoniz

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Re: Merc oil vs Mobil 1

Dont marine engine oils have anti rust additives which may not be present in automotive oils like Mobil 1?
 

Merc4ever

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Re: Merc oil vs Mobil 1

Nothing can rust when covered in pure motor oil so I would have to say that pretty much all oil is anti corrosive.
 

QC

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Re: Merc oil vs Mobil 1

GM said to use 5W-30 back then when it was in their vehicles.
Be careful with this statement as this has more to do with fuel efficiency and beating the competition for ratings on the sticker, heck some are recommending 0W30 now. Marine engines, and generally loafing automotive engines, do not live in the same environment or deal with the same loads, speeds etc . . . ;)
 

wca_tim

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Re: Merc oil vs Mobil 1

ditto on be careful regarding the thinner oils in particular... the engines spec'd to run those have differenc clearances. you would prefer a boat to have larger bearing and piston clearances and run thicker oils...

just don't get down hard on it until it comes up to temp - especially with thicker oils. I run mobile 1 15-50 in my boat... of course it's built a little loose....

Just about ANY oil that is checked often and changed regularly is better then the very best oil that isn't changed, etc...
 

Gary H NC

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Re: Merc oil vs Mobil 1

Straight 30 weight.Rotella has always been a good oil.Sold at most any auto parts store or truck stop in SAE 30. About 12 bucks or so a gallon.
 

JustJason

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Re: Merc oil vs Mobil 1

Ken 23434 said:
I had a 2001 TT also. I always used the Mobil 1 Racing 4 (no T) from Autozone. I now have the 2006 Daytona 675. It calls for the same oil and now the Mobil 1 at Autozone says "4T". Not really sure what changed in it.

That's what I had also, an 01 that I bought new in 00. It was one of the sharpest looking bikes I ever owned. Beautiful caspian blue. Had the solar cover and the actual Triumph race can... It was also 1 of the loudest bikes I've ever heard with that pipe on it.
Back when I bought the bike I called Triumph in England and talked to the guys over there. They told me that their special 4T racing oil was Mobile 1 in their own bottle, for whatever that's worth.
 

Simoniz

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Re: Merc oil vs Mobil 1

Nothing can rust when covered in pure motor oil so I would have to say that pretty much all oil is anti corrosive.

And if you leave your engine sitting for 6 weeks in a moist marine environment, how long do you think certain parts are going to remain covered in oil?

The oil will quickly drain down to a very thin film indeed and then you have the parts at the top end (upper piston rings, cylinders, valve stems) where there was never much oil to begin with.
 

Merc4ever

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Re: Merc oil vs Mobil 1

Straight 30 weight.Rotella has always been a good oil.Sold at most any auto parts store or truck stop in SAE 30. About 12 bucks or so a gallon.

Isn't straight 40w what merc recommends for summertime temps? At least that's what I have read.
 

QC

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Re: Merc oil vs Mobil 1

There is no sarcasm intended with this (gee, I sure seem to write that a lot, hmmmmmm) . . . Why is the manual's recommendation important with the 40W thing but not the rest of it?

BTW, I run Mobil 1 now, and I am using the 15W50 this season, I used the 10W40 last year. I run in 115 degree ambient often, so I talked myself into it. Nothing more than a simple debate while standing in the oil section at Wally World . . .
 

Don S

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Re: Merc oil vs Mobil 1

Isn't straight 40w what merc recommends for summertime temps? At least that's what I have read.


Merc lists several oils that can be used, and in the order of preference.
Here is a link to the Mercruiser site. Read the whole oil recomendation section of the link, not just the big words.

http://northamerica.mercurymarine.com/serviceandwarranty/mercruiserfaqs/fueloil.php

This thread is like every other oil thread. Every DIYer seems to know more about what oil to use in their marine engine than the manufacturer. However, that same DIYer can't explain the basic principals of how an engine works, yet he knows all about oil.
Kind of funny really. If some DIYer uses XYZ oil, and the engine didn't blow up the first time out, then it must be the best oil in the world, and he will recommend it to everyone saying it's the best thing since sliced bread. Then he looses his engine the next year with a cracked block because he didn't have the sense to winterize properly.
 

45Auto

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Re: Merc oil vs Mobil 1

QC said:
so I talked myself into it. Nothing more than a simple debate while standing in the oil section at Wally World . . .

Yeah, but that debate wasn't really fair. You were engaged in a battle of wits with an unarmed man ...... :)

You're lucky that you didn't end up with transmission fluid or axle grease in it!
 

Merc4ever

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Re: Merc oil vs Mobil 1

Merc lists several oils that can be used, and in the order of preference.
Here is a link to the Mercruiser site. Read the whole oil recomendation section of the link, not just the big words.

http://northamerica.mercurymarine.com/serviceandwarranty/mercruiserfaqs/fueloil.php

This thread is like every other oil thread. Every DIYer seems to know more about what oil to use in their marine engine than the manufacturer. However, that same DIYer can't explain the basic principals of how an engine works, yet he knows all about oil.
Kind of funny really. If some DIYer uses XYZ oil, and the engine didn't blow up the first time out, then it must be the best oil in the world, and he will recommend it to everyone saying it's the best thing since sliced bread. Then he looses his engine the next year with a cracked block because he didn't have the sense to winterize properly.

Well I never boat when the air is under 50 deg. So the only oil for me is straight 40 from Auto Zone unless I want to go to the Merc dealer.

How can you argue with the maker of these great boat movers?
 
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