Shell Rotella T6 5w40 for a 1999 5.0Liter TBI

[evantful]

I posted this over the Volvo section as this technically relates to a Volvo Penta 5.0GI I own, but I figure there are a great number of Merc owners with information.

I know the oil subject has been beaten to death, so what Im asking if anyone has any experience using Shell's fully synthetic T6 5w40. I know a lot of people that swear by the conventional Rotella 15w40, but I have been running synthetic since the boat was new (just passed 600hours) and despite Volvo's lack of clarification and telling us (per their service bulletin) older gas powered Volvo owners to just use their 15w40 VDS-3 Diesel oil (which is a non synthetic) after years of recommending only synthetic SAE30,or pure synthetic 20w-50, 15w-50. Frankly I think Volvo will sell what keeps their SKU count the lowest.

I would use mobil's 15w50 synthetic, but I think a 50 weight oil ,even after shear down, on a non-carbureted, would be a little thick for my needs in a 5.0 liter engine that is fuel injected and not run 'hard'. I can see the guys running the big block 7.4/8.1 or top end 5.7's maybe needing it.

Has anyone started using the 5w40 T6 in a marine application?

 

[H20Rat]

I use nothing but rotella t6 in almost all my vehicles year round. It is probably one of the best oils out there, and handles extreme load/pressure better than most others without shearing down.

 

[Bt Doctur]

5W is a bit thin for sustained running. car engines do not run pedal -to -the -metal all day long.
If you think it is that good, try running your car in first gear on the highway for a few hours.

 

[evantful]

The 5w rating is the only thing that is giving me pause on using it. I know Merc and Volvo typically like oils that have a closer Cold flow and Operating Temp rating (i.e 20w40), but at the same time isn't the 5w spec irrelevant as I would only be using this in temps above 50F (mostly 70-85F)?

The reason why I would consider using it despite the 5w rating is because this oil is also used in High RPM constant load diesel machinary

 

[bruceb58]

Unless Merc or Volvo comes out and says to use an oil as low as 5W, I wouldn't. I use 15W-50 Mobil 1.

 

[Lou C]

And since the other real common marine spec oil (Pennzoil Marine) comes in a 15w/40 grade, that seems to be a good choice. I would not worry about not using syn in a boat engine. I don't think you hit the oil temps that require it, unless you are running close to wide open much of the time. I just did a quick check of my oil filter temps using Merc non syn 25/40 oil and after running on plane, I get 180-200*F measured on the filter...not sure if thats typical but it seems well within the ability of the oil not to break down.

 

[midcarolina]

The 5W means absolutely nothing to the vast majority of boat owners...... as that is just a measurement of how the oil will flow in extreme cold conditions at start up........the W stands for winter.........

 

[Lou C]

Well....it does in a way you might not think of, at least for conventional oils. In order to make a non syn oil span a wide viscosity range like a 5w/30, they have to add viscosity index improvers to make the oil work that way. The problem is that they break down over time and that causes shearing of the oil, to a lower viscosity. This is why the OEM's used to recommend straight weight oils (ie straight 30 or 40) before syn marine oils were available. Merc says that their 25w/40 does not use VI improvers, and that is how it is supposed be better than a conventional oil. Another factor in the mix, is if you have an engine oil cooler. In that case you could use multi vis oils without the risk of breakdown. But on an engine with no oil cooler, I think you are better off using what the OEM tested in your engine. Unless you do comparison testing with identical conditions there is no way to know, if the oil is breaking down, unless you see it in low hot idle oil pressure readings.

 

[bruceb58]

If Volvo recommends that viscosity oil, use it. Just so you know, they don't.

 

[evantful]

If Volvo recommends that viscosity oil, use it. Just so you know, they don't.

Certainly they do not mention a 5w40 synthetic HDEO. But at the same time they never mentioned ever using a 15w40 HDEO conventional oil either, until 2011 when that became their recommend replacement for Volvo Penta engines produced prior to 2008 via a Service Bulletin (see attached link) .

View attachment Volvo Penta.pdf

I guess thats part of where my discussion with this is going. Volvo's recommendation went from: Conventional 30w SAE (Mid 90's) to Full Synthetic 30w SAE (Late 90's til discontinuing in 2010), and in which cases the 30w was unavailable to use a Full Synthetic 15w50/20w50, now to finally 15w40 VDS-3 Volvo Branded Diesel Conventional Oil.

 

[HT32BSX115]

Well....it does in a way you might not think of, at least for conventional oils. In order to make a non syn oil span a wide viscosity range like a 5w/30, they have to add viscosity index improvers to make the oil work that way. The problem is that they break down over time and that causes shearing of the oil, to a lower viscosity. This is why the OEM's used to recommend straight weight oils (ie straight 30 or 40) before syn marine oils were available. Merc says that their 25w/40 does not use VI improvers, and that is how it is supposed be better than a conventional oil. Another factor in the mix, is if you have an engine oil cooler. In that case you could use multi vis oils without the risk of breakdown. But on an engine with no oil cooler, I think you are better off using what the OEM tested in your engine. Unless you do comparison testing with identical conditions there is no way to know, if the oil is breaking down, unless you see it in low hot idle oil pressure readings.

Absolutely right.

AND while a multi-grade mineral oil starts out as a low weight oil (I.E.a 5w) and uses VI improvers to "make" the higher grade when hot, A synthetic IS the higher weight oil that doesn't lose viscosity when "worked" like a VI "improved" oil does with use and doesn't thicken much as temps drop......

Shell Rotella T6 5W-40 acts like a 5w at extremely cold temperatures, it IS always a 40W oil @ 100C like any other 40W oil.

So, when your boat is completely FROZEN in place @ -50F in the lake, the engine will still crank with 5W-40 in it.......... I am not sure how that's a benefit for me, I only boat when I can swim in the lake without a wet or dry suit!!

 

[evantful]

Absolutely right.

AND while a multi-grade mineral oil starts out as a low weight oil (I.E.a 5w) and uses VI improvers to "make" the higher grade when hot, A synthetic IS the higher weight oil that doesn't lose viscosity when "worked" like a VI "improved" oil does with use and doesn't thicken much as temps drop......

Shell Rotella T6 5W-40 acts like a 5w at extremely cold temperatures, it IS always a 40W oil @ 100C like any other 40W oil.

So, when your boat is completely FROZEN in place @ -50F in the lake, the engine will still crank with 5W-40 in it.......... I am not sure how that's a benefit for me, I only boat when I can swim in the lake without a wet or dry suit!!

So thats kind of what Im getting to is that, because I will be operating in outside temps above 50 degrees, the 5W rating is irrelevant. The oil, even when I start the engine will be nearly a 40 weight, and given that the T6 is a modern Full Synthetic AND HDEO oil designed for high stress environments, there isn't much risk of shear down like a more typical automotive multivisco oil would. Even if it sheared to a 30 weight towards the end of the OCI, its still fine as that was what is called for by Volvo

 

[HT32BSX115]

The original argument still applies.........ALL types and grades of automotive oils have been tried in marine engines. They pretty much all worked.

Almost NO marine engines fail because of oil (except "lack-of")

Most marine engines fail or have short lives because of general lack of service (and in cold climates, freeze damage)

You're pretty much free to do whatever you want.......... if you choose not to use what the manufacturers recommend, you'll likely get away with it.

Ask 10,000 people on any automotive, marine, lawnmower, tractor, outboard, specialty car opinion forum site what they use and you'll get nearly as many different answers on what works for them or what their uncle, pet mechanic, diesel mechanic, dad, brother, mother, great-great aunty uses.

I don't know if there's a LOT of benefit in that sort of effort though.........


Regards,


Rick