Kanookstr

Merc says not to use synthetic oil because they don't Make a synthetic oil. The day merc puts there synthetic brand on the shelf. They will recomend it!

ursus

Merc recomends the Use of 25W40 if using a multigrade. The reason for this is Marine engines run cooler then their automotive counterparts, remember the numbers are SAE (automotive) ratings. 25W40 will be a 25 weight when cold and 40 weight when hot. 25W40 will be at least a 30 weight when the engine is running at the low end of its temperature range, which at cruise speed they can do for extended periods of time. 15W50 on the other hand may only be 20-25 weight, a little lite, and 5W50 can be as lite as a 10 weight when running at the cool end, 10W40 will also be pretty lite when you are just putting out from the dock that 1st 1/2 hour after startup. Maybe not a problem if you run fast/hard all the time but that is the real reason they don't reco synthetics because they are not available in a 25W40 blend. Merc reco's an oil that will be ok under most all conditions cold and hot, hard running or easy cruising.

CAP071

I run straight Valvoline VR 40 I was told that is ok?

turbo2256

Thought I saw a Merc synthetic oil at the dealer the other day maybe was 2 stroke stuff though. The only bad I have heard was from Crane said something about roller lifters sliding right down the ramp with out rotating roller and causing wear voiding waranty ,,, I run synthetics in everythig that dosnt leak it.

BajaBoss252

What grade of Mobil 1 are you guys using?

27 FOUNTAIN

Been using Mobile One 15w50 on a fresh engine for 100 hours, so far so good. Used regular oil first time out.

MikeStar

Mobil pure synthetic 15W-50 in my 502, two trouble-free seasons. Heard from more than one source that Merc says no synthetic because there's none with a Merc label - and that doesn't surprise me a bit.

99baja342

If you are changing the oil and filter every 15-20 hours (like you should be on these engines), I do not see how Mobil 1 syth. 15w-50 would be that much better for an engine compared to Valvoline VR 40. The Valvoline VR 40 is good quality racing oil. The price is not justified for the Mobil 1. Now, if you do not change your oil and filter every 15-20 hours, then you are hurting your engines and NO type of oil will stand up to this abuse.

If you feel better spending the extra money for Mobil 1, good for you.

A quick story....Many years ago, I had a boat that had almost 1,000 hours on it. Yes, I said 1,000 hours. It only ever had petroleum oil used in it. But, the oil was changed on a regular basis. I sold the boat and last I heard, it is still running great!

The bottom line....use quality oil (synthetic or petroleum) and change it often!

blue thunder

My cruiser has sslightly under 1000 hours on it now and it is quite healthy. It runs a sbc Volvo. I've been using castrol straight 40 in that all along. The change interval is 50 hours. Course I never run that engine hard.

Other boat I am going to try the Mobile 1 15-50w in to see what up with that. I put in oil temp gauges to help my evaluation. Next time out I will have castrol in one engine and mobile one in the other. It'll be interesting to see what happens to oil temps and pressures.

BT

Jayl13

How many quarts do these things hold anyway?
5-6-7?
standard 454-330's
Thanks
Jason
PS been running Mobil 1 in my TA (ls1 engine) since '99
Pulled out the cam and installed GM hotcam
Cam bearings did not have a blip on them,
stock cam had discoloration but not one score, scratch, line, irregularity whatsoever
I was impressed
Not sure what Oil Im going to use in this but going to stick to 10W 40 for marine temps dont get as high as car temps
Break down is not as immenent
20w50 too thick for this since average temps wont get near cars temps.
5w30 too thin, does not run low rpm's
40 is right smack in the middle

Jason