30 weight or multi weight oil

[SGY]

Ok. I'm sure this has been covered a dozen times but my mechanic who winterized my boat insists upon 30 weight oil. He says that he has seen engine failures using the mult-weight oil. Problem is, the manual for my 2003 PCM Excalibur says 15W-40 for operation above 50 degrees. What should I do? Do I trust my mechanic who has been working on inboards for 30 plus years or do I put the recommended oil in. BTW, I always put 30 weight oil in my GT-40 with no problems. (I think that was recommended by PCM.)

Thanks for your help.

[skinautique]

RE: 30 weight or multi weight oil

Trust the mechanic and use straight 30 or 40 weight high performance oil.

[FatBoy]

RE: 30 weight or multi weight oil

Then why would PCM recomend otherwise skinautique?

[NautiqueJeff]

RE: 30 weight or multi weight oil

Several trusted mechanics and PlanetNautique members have recommended straight weight oil in the past. I trust their opinions, but I would like clarification on why they are saying that people should use different oils than what PCM recommends.

As for me, I'll use what PCM recommends, so that there isn't any question when it comes to warranty issues.

[skinautique]

[Franz]

Did I read something wrong or does the GT-40 manual call for 40 wt?

[FatBoy]

I would go with whatever the owners manual says.

[TrailInn2]

My dealer recommends 15-50 racing oil, any opinions or experience with this?

[jedgell]

What is the benefit of running a straight 30 or 40 WT oil? I've been using 10W-40 in my GT-40. Does the 10W-40 offer less protection? What are the real differences? Thanks in advance, I don't want to keep using the 10W-40 if its hurting my boat.

[nms1991]

I recommend using what PCM recommends, I know the ZR6 needs 15w40 but the Excalibur can use straight weight. Just use a good quality oil.

[JJ]

SGY,
I recommend using what PCM states in the manual. PCM works directly with GM on the design and applications of their engines. They know which oil viscosity works best for their engines and the loads put on them. The best thing you can do for your engine is change it more often then required. That is why I change oil and filter every 25hrs instead of 50.

[SGY]

Thanks everyone for your help.

JJ, did you get your boat yet?

[JJ]

It's sitting at MWCC waiting for the bimini and cover. They said I should have it at the end of the month. Are you going to be in KC anytime this year?

[MARK-S]

SGY, Do you have open water yet?

[83sn2001]

Your Excaliber is a gm block. gt-40 is a ford block. The reason for the multi weight oil is because of clearences inside the engine. You run the risk of bearing failure if you use straight weight oil in newer engines. PCM doesnot build the engine, GM does. My Late model Chevy truck specifically says no straight weight or high viscosity oil(20w-50 ,etc.)