Penrite 10 Tenths for Mercruiser

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Fella's,

Whats your thoughts on using Penrite Racing 10 Tenths 15w/50 in a pair of 2006 8.1 Mercruisers (with oil coolers but no cats).

Specs are as follows:

Kinematic, cSt
at 40°C 114
at 100°C 17.5

VI 169

Ca 2960 PPM
Boron 630 PPM
Zn 1680 PPM
Phos assumed at 90% Zn 1,512 PPM

Noack 5

Base Number 9.8

HTHS 5.28cP

SN/CF A3/B3 rated and can be used in light duty petrol and diesel engines up to 2008 where A3/B4 is specified.

Claims to be shear free with no friction modifiers with POA and Esters.
Claims to be suitable for "normal" on road applications in a wide range of vehicles which suggests it would have a normal service life as also suggested by the base number and HTHS.

Suggests can be used where 15/40 or 20/40 oils are specified so it's closely in line with the Mercruiser spec'd 25/40 oil.

Currently using the Mercruiser 25/40 synth blend and previously the 25/40 mineral. In both cases the 8.1's start to use oil after about 20 hours and progressively gets worse (although with normal usage) until the next change. I'm assuming the oil is shearing and thinning over the year. Comments from other boaters indicate this oil shears to a 20w with nominal use.

I've read where others boaters has switched to Mobil 1 15/50 in these motors and consumption stops although reports also shows the 15/50 still does shears to a 30w.

Do approx 50 - 70 hours a year

Local temps don't go below 0 degrees C and up to 40 to 45 degrees C.

The oil is cheaper than Mobil 1 and Amsoil equivalents and also the Mercury 25/40. Yes the diesel/API rated oils from the majors are cheaper.

On paper this oil looks to be up to the task.

Thoughts, comments and advice welcome.
 
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Looks up to the task - but suprised the Merc lube shears when one looks at what that stuff gets run in - Merc stays away from VII as well. In any case your choice supports that philosophy and carries a nice set of numbers.
Check your dipsticks for foaming after the first hard run - happy boating
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Cheers for the comments 4WD

Yes the Merc product data does suggest no VI so I can only assume the base oil isn't up to the task and/or there is fuel dilution. I've never been able to find specs on the Merc oil but there is speculation this is a blend of straight weight 25 and 40 in what proportion who knows - but assuming 50/50 would equate to 32.50 weight which is more or less in line with Mercs other recommendations of a 30 weight oil then a 40 weight oil depending on temps. Therefore, if it starts out as a 32.5 weight shearing to a 20w is is plausable.
 
A UOA will tell you if it's shearing.

What about Rotella T or T6.

A boat engine is used more like a diesel engine, constant RPM hour after hour. Many boaters I know are using Rotella T.
 
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Donald,

Unfortunately, no Rotella T or T6 down under (Australia) we have Rimula versions instead and I'm not sure whether the composition is the same as the Rotella.

But I hear what you are saying, plan B was to look at diesel oils in the 15w/40 weight such as Delo 400 multigrade, Delvac 1300 super or Rimula. I would prefer a synthetic diesel oil but most seem to be less than a 15W and are generally thin 40 weights. I'm not sure I want to go much lower than 15W down here and Merc oil is 25W hence my original Penrite choice.
 
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I reckon you could use the Racing 10W40...same basic premise.

Penrite, same add pack, shear free formula, robust HTHS, and if you need to thicken it, the 15W50 is totally compatible for the same reasons.
 
I reckon you could use the Racing 10W40...same basic premise.

Penrite, same add pack, shear free formula, robust HTHS, and if you need to thicken it, the 15W50 is totally compatible for the same reasons.
 
I'd run 10/10ths any day in a marine application. No CATs, no worry
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If it's warm enough to go boating, the 15W or 25W is entirely adequate for cold start
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DoubleWasp - I'm assuming your talking about the 20w50 VR1, can only get the 10w/40 VR1 down under. The other alternative is 20w/50 Maxlife (red bottle).
 
the Maxlife is a possible alternative. Depends on cam and lifters. Flat tappet cam I'd run 10/10ths or VR-1. 10W-40 would be fine if the motor has any reasonable bearing clearances ...
 
The 8.1 has a roller cam (basically a marinised GM 8.1 Vortec motor). Not sure I'm keen on a 10w40 given Merc specs 25w/40 oil. My local conditions also don't warrant a 10W oil.

My only concern with the 10 Tenths is whether it contains sufficient corrosion inhibitors as the boat lives on the water 24/7 - otherwise the specs look good.
 
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The inside of all engines that run periodically is completely covered in oil film. Even old dead marine engines that are sitting in the bone yard will be mostly rust free inside unless they get standing water in the actual engine ...

That corrosion inhibitor stuff is mostly marketing. Before the 1990's nobody talked about "extra" corrosion protection. I've never seen a marine engine rust from the inside, including ones that were sunk in salt water, brought up, flushed with diesel, re-oiled and fired up.

Raw water cooled in the ocean, sure. They loose water jackets and start pushing salt water into the motor. Have seen many exhaust manifolds eaten through. But the inside of a fresh water cooled or heat exchanger engine - nope.
 
So I stumped up and bought the Penrite Racing 10 Tenths 15w/50 - plan to do a service in the next couple of weeks.
 
So it's in but didn't get a chance to take it for a run as I was a bilge rat for most part of the weekend.

Initial observations reveal this oil provides a hair over 50 psi at cold idle (650 rpm) which is in line with merc's 25w/40 oil......so far so good.
 
I got the opportunity to take the boat out for a decent run over the weekend. This oil has slightly more pressure than the 25w/40 at cruising rpms as expected i.e. around 55+ psi and drops back to 25 psi after coming off the plane at 4,000 rpm's back to idle rpm's which again is in line with the behaviour of the merc 25/40. It did recover quickly back up to around 55 psi. Overall, this oil seems to behave in a similar way to the merc 25/40 albeit with a tad more oil pressure at most rpms as expected.

The 11 year old motors didn't spring any new oil leaks with the POA/Ester based oil - although I do have to install new gaskets and o-rings at the remote oil filter adapter on both blocks to fix an existing oil weep. I've not noticed any difference in cranking speeds nor any difference in engine noise on startup.
 
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