What Oil?

[Henner]

I have been reading and reading through the threads on which oil is the best for our 351 pcm motors. From what i have read a lot of people were running Rotella 15-40 and then i was seeing threads where people were saying don't run rotella anymore due to our flat cams and etc... I have a 90 ts6m with 627 hrs on it so what would be the best oil recommendation??

Thanks,

[michael hunter]

I run Mobil 1 15w50 its good for both roller and flat lifter engines. I also use the Mobil 1 of K&N filters

[TitanTn]

Michael's suggestion is not just because of the oil quality, but also because it contains ZDDP for flat tappet engines like ours. You can follow his recommendation or you can add a ZDDP additive to the oil of your choice.

[chris young]

I've been doing a lot of reading on the subject lately, and I'm narrowing down my choices. I settled on Mobil 1 high mileage 5W30 until I discovered I couldn't get it in Canada. I'm re calibrating and looking again. I would most definitely pick a high ZDDP oil if I could, but there is enough evidence to support that once the engine is run in, that a reasonable amount of ZDDP should be ok for our motors. Unfortunately it seems that it's only the higher grades that seem to have the high ZDDP, and I'm more concerned about running too thick an oil than I am ZDDP. The Mobil 1 high mileage has proportedly an excellent additive package with seal conditioners, decent ZDDP levels and apparently a really good de sludging ability which was why I was choosing it. There are also those that swear by marine oils, but I still haven't been able to find out why.

If you want to go down the rabbit hole www.bobistheoilguy.com. Some of the guys who actually formulate the oils for the manufacturers are frequent posters there. There's almost too much info.

[michael hunter]

Just to add 1 thing the 15w50 is the weight that has all the additives if you are going with Mobil 1 use the 15w50.

[Ptownkid]

Would this recommendation also be true for a 1992 454?

[chris young]

I would say yes. I still think for older boats the high mileage formulations might be a bit better. Zink and phosporus (ZDDP) in the M1 15W50 is the highest at 1300 and 1200 ppm respectively, but the HM oils are still quite high at 1100 and you get the seal conditioners and de sludging capabilities as a bonus. I'd be trying it for sure if I could get it, but it's not avail in Canada. You can compare here; http://www.mobiloil.com/USA-English/MotorOil/Files/Mobil_1_Product_Guide.pdf

Does your boat have a catcon? Thats the only significant reason I can find for not using a high ZDDP oil, and even that is open for debate. (Apparently if you're burning oil the phosphorus can harm the cat) Since we're both in Canada, when I find something comparable, I'll post it here. The only thing I don't like about the 15W50 is the high viscosity. It may push the oil pressure too high, but the only way to know is to use it and watch the oil pressure. The recommendation I found is oil pressure should be about 10psi per 1000 RPM. If it's higher than that you may not be getting the flow needed for proper lubrication.

[TitanTn]

Thanks for that Chris. I understand that the psi recommendation is an approximation, but I'd be nervous if my fast idle (1000 rpms) was only 10 psi. And even 30 psi for 3,000 rpms seems a little low.

[chris young]

I hear ya, and I'm by far no expert, I'm passing this along.

The recommendation came from an oil industry guru in a white paper that he called "oil university". While I believe he's a formulator, I've read enough of his posts and the 10 page white paper that I'm pretty confident in this recommendation. The point he makes is that flow (circulation) is the goal, not pressure. High oil pressure likely means low flow. The oil performs not only lubrication but cooling as well, so high flow benefits both. In this case we're manipulating oil pressure by playing with the viscosity. So getting higher pressures means that the oil isn't flowing. I think we all perceive high oil pressures as evidence of a tight motor so that's what we want to see on the gauge, but I think a better way to look at it is what pressure with what viscosity? We can all get nice high pressures if we put thick enough oil in there, but it certainly wouldn't be an indication of a tight motor.

I'm getting way outside my comfort zone here but I'm going to put this out there for the proper motor guys to comment on. Higher pressures may be of some benefit for journals, but cams and cylinders won't. Also IIRC, the 10psi rule is for the high RPM range, ie it won't be linear, but we'd like to see 40 psi at 4000RPM

[TitanTn]

I agree with everything you said Chris. And I think was I was alluding to in my previous post was what you said in your last sentence. That it's likely not linear, but 40psi at 4,000 rpm sounds healthy.

[chris young]

A little extra flogging of the dead horse, this is a similar discussion on the oil forum, based on this I think I'll try a full synthetic HDEO 15W40 as my starting point.

http://www.bobistheoilguy.com/forums/ubbthreads.php/topics/3322032#Post3322032

[Ptownkid]

Too bad they don't carry the walmart version in Canada...

[chris young]

Good news, I dropped by Part Source last night and low and behold they do sell the M1 High Mileage, 10W30 so I'm going with that.

[Ptownkid]

I thought the consensus was to go heavier?

[whammond]

Looking at the PCM Service Manual (Pg 192 is the engine lubrication info):

http://www.planetnautique.com/CorrectCraftManuals/PCMsvcmanual.pdf

It looks like 10W-30 or 10w-40 may be the way to go.

[chris young]

I thought the consensus was to go heavier?

I'm not sure whether the boat will need 40 or not, I'll monitor oil pressure with the new oil and if it's low I'll get some heavier stuff. Also, I wanted the seal swelling and desludging that the HM offers for at least one, maybe 2 oil changes, and then I'll likely go over to the HDEO. The other reason for choosing the HM was that I know what's in it, and now I'd have to research all the available HDEOs available to come up with a good choice.