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Engine Oil

Old 02-18-2004, 06:02 AM
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Default Engine Oil

Mercury says 15w40/

Some use striaght 40 wt....

I found Mobil- 1.. 15w40 or even 10w- 30 to do a better job...especially faster lube on starting up

Custom engine builders of 600Hp and up say Redline Synthetic is the only one to keep warranty in's a 10w-40...Callaway Corvette says to use it on 383 strokers stuff around.. it time for stnthetics? Why is Mercury still pushing thick non-synthetics that eventually breakdown sooner and provide less protection on starting where most wear can occur?
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Old 02-18-2004, 07:05 AM
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Location: Naples, Maine
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Merc recommends their own blend 25-40 oil. The merc oil is not a true multi-grade oil, it is just a blend of 25 w and 40 w oils. A true multiweight oil would start out as (if 10-40 for example) 10 weight and they add viscosity improver so it will behave like a 40 weight when warm. The problem is as these multiweight oils break down over time and marine engines run hotter oil temps the viscosity improvers break down and you are left with a 10 weight oil.

I believe that Merc recommends straight 40W if not running the Merc 25-40 blend.

I'm running 20-50 because of the cold water temps up here. It takes too long for my oil to come up to proper operating temps.

The debate over synthetics vs petroleum oils will continue...

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Old 02-18-2004, 08:20 AM
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I agree....I've been running straight 40 as well.....switching to Mobile 1 15/40 this spring. From what I've gathered from the debates on here.....synthetics will do a better job.
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