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Gt40 oil change


rodltg2
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@rodltg2 that is what they primarily sell it for, but many boat owners and dealers use it. My Indmar specs 15W40 Marine Pennzoil which is nearly impossible to get this year for some reason. Rotella seems to be what most folks have been using anyways since it meets all the required specs (SM CJ4). Some of the earlier versions of Rotella had a warning about use with catalytic convertors but the current T4 15W40 does not.
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As far as the weight goes 20W50 is fine. A lot of gearheads would say it's better. The bigger issue is the 351 has flat tappetts that requires additives that are missing in most modern oils (zync something if I recall). VR1 is one of the few oils that has the additives the GT40 needs and probably the best choice overall.

 

There was a long discussion on this a few years ago and is probably in the archives if you are really interested.

If it was easy, they would call it Wakeboarding

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B.O.S. normally avoids Oil Threads.

 

My theories (not an oil specialist) usually run towards the concept that straight weight oils hold up best due to the lack of modifiers. A 20-50 is 20 weight oil that has modifiers inside it that make it act like a 50WT oil when hot.

 

So 20-50 probably OK, 40 WT probably very good oil for the application - I would bet that if you run in very cold water that you might want to run a 15-40 or 20-50 just so that the start up is easier.

 

When I used to run old BMW motorcycles those were the worst oil shamers. Would buy everything from Kendall to VR-1 to specialty formulations. Ultimately I switched to Rotella T as well even though many claim it doesn't have as much ZDDP as racing oils.

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He is correct. Somewhat academic.

 

Racing oils can have great levels of the good stuff, antiwear additives. Which we like for keeping our cams in good order.

 

They don't however need to have additives which control how corrosive the oil becomes as it ages. Consider it like a pH buffer in chemistry. Road oils need to protect a mildly used engine against months of cold starts around town use with few instances of heavy use. Over that time the additives need to prevent moisture and contaminant build up from causing damage - including having detergent levels to keep stuff moving into the filter.

 

Race engines need the opposite - tons of antiwear additives in oil that is changed after the race and never sits.

 

 

Rumor has it that rotella and other diesel oils like Delo have cut zddp with the addition of cats and def over the years which... I use rotella anyhow I'm cheap and it's on Amazon prime subscription so it shows up with a filter right before I winterize.

 

I doubt anyone will have an issue with vr-1.

 

Maybe a poll but I'm sure this forum has thousands of cumulative hours of engine running.. anyone wear out a cam? What oil was it?

 

 

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@rodltg2 The Valvoline 20w50 you pictured is better for your engine than the rotella. Not saying rotella is bad oil, I currently use it in all my diesel engines, but the zinc level is lower in it than in previous years. This is why most will recommend rotella. Another good recommendation for your engine is Mobil one 15w50, also high in zinc additive for your flat tappet cam engine.

 

Main thing is you care about maintenance, no matter which oil recommendation you use, regular maintenance is by far the most important! Oh, and don't use fram oil filters ;)

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But the PCM GT40 service manual says PH8A (Fram) specifically!

 

It actually does, but I know what you're saying. The Motorcraft FL1A is regarded as one of THE best oil filters in that size. I researched it a ton when I was racing 351W engines, and always ran Motorcraft filters.

 

An interesting link from a long time ago where a guy cut apart about 30 different filters and looked at the construction and size of filter media: Filter study (Short link just for @Horton :smile: )

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It says right on my oil filler cap 15w40. '08 196 with 5.7. So I use diesel oil. Sometimes Rotella , sometimes Mobil Delvac. What Nautique recommended for the GT40 I don't know. Doesn't it say on your cap? I've know of a couple of guys who use synthetic, put 50-60 hours a year on a boat and then change it at season end anyway. A waste in my opinion,
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owners manual on my old GT40

powered SN said "40w40." Straight 40 doesn't work in the north when skiing in November, so I always ran 15w-40 Castrol GTX which has 1300 ppm of zinc...

 

don't let the diesel label fool you on the various 15w-40 brands - the fine print states it's good for conventional gas automobiles as well.

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