Engine oil for I/O's

[keithkz]

What viscosity oil are you guys putting in your I/O? I have the (2005 year) 5.7L Volvo Penta (280 HP) which is basically a 350 Chevy. I changed the oil myself 2 years ago and honestly cannot remember what I used other than it was Mobil 1. I have the engine manual and in the chart it lists 30W, then 20W/50 and then 15W/50 for outdoor temps 32 degrees and warmer. You can't get Mobil 1 in 20W/50 but you can in the 15W/50. Here's the kicker though.....to the right of that chart in my manual it says:

"Use single viscosity oils in markets where available. The use of multi-viscosity oils such as 10W-30 and 10W-40 is not recommended unless single viscosity oils are unavailable."

Straight 30W is what I use in my push lawnmower and I was also told this weight oil does not have a detergent and I shouldn't use it in a big engine like I have.

So what should I put in it?

 

[gnc1017]

What viscosity oil are you guys putting in your I/O? I have the (2005 year) 5.7L Volvo Penta (280 HP) which is basically a 350 Chevy. I changed the oil myself 2 years ago and honestly cannot remember what I used other than it was Mobil 1. I have the engine manual and in the chart it lists 30W, then 20W/50 and then 15W/50 for outdoor temps 32 degrees and warmer. You can't get Mobil 1 in 20W/50 but you can in the 15W/50. Here's the kicker though.....to the right of that chart in my manual it says:

"Use single viscosity oils in markets where available. The use of multi-viscosity oils such as 10W-30 and 10W-40 is not recommended unless single viscosity oils are unavailable."

Straight 30W is what I use in my push lawnmower and I was also told this weight oil does not have a detergent and I shouldn't use it in a big engine like I have.

So what should I put in it?

I'll let others chime in here too but we always used Valvoline SAE40 Racing Oil in our previous 454 I/O runabout. We used dino oil, not synthetic. Nothing against Mobil 1 but the recent buyer insisted on a compression test before signing off and while only ~500 hours, all cylinders read extremely well. Although cost difference between the Valvoline Racing Oil and Mobil 1 may be minimal, if anything - just maybe another option if you can't find the viscosity you're looking for which I agree is important. Note that we are further south than you (St. Louis area) and didn't run the boat in cooler temps, if you want to take that into consideration.

And on many or most motors, you may not want to run synthetic in anything that isn't fully broken in (to ensure proper ring seating) but double-check with manufacturer specs on that. In the end, since you likely are more concerned about mechanical failure (probably would be due more to abuse than you wearing it out and since you asked this question, doubtful you are an 'abuser'), I'm sure either is fine as long as you are using a quality product. Again, maybe another alternative for a non-sythetic.

FYI - I always use Wix filters (also can be purchased repackaged as NAPA Gold, the high end Car Quest version, etc. - should say so on the box). I cut a new Fram in half years ago and wouldn't put that on any engine, assuming they haven't significantly changed their design but that was enough for me. I run my vehicles 300k miles plus (pretty much until they are impractical for my use, not because they are shot), all the time never using synthetic (again, not that there's anything wrong with that and can understand the benefits for certain users). Just saying that a quality filter can make a difference which you may have already knew. Of course, the OEM manufacturer filter is good too and wouldn't discount them but if you are considering or want another option than OEM, I just became a believer over the years in Wix oil, transmission, fuel, etc. filters. To me, they are the 'Bennington' of filters  and my vehicles are proof positive.

 

[JeffS]

There was a time in the early 2000's, when for some reason, mfr's were recommending single viscosity oils. Current recommendations that I have read, are back to multi-viscosity oils...even for older engines that were previously recommended single viscosity. When I had the big twin Crusader 7.4's in a previous boat, I ran synthetic Rotella 15w40. I would run about 60 - 70 hours a year, which equated to about 1800 gallons of fuel. I had no issues with anything oil related. It's all personal preference...and I don't think there's a right or wrong answer. A top-tier filter and frequent changes with high quality products usually yields great results.

 

[gnc1017]

A top-tier filter and frequent changes with high quality products usually yields great results.

Obviously, totally agree!

And multi-visc. may actually be preferential if you do an 'extended' boating season. You be the judge but as Jeff said, other things are likely more important.

 

[keithkz]

I just called the dealership and they said that Volvo's full synthetic is 10W/30 so I'll get Mobil 1 in that. Thanks everyone.

 

[Wild and Free]

Other than small engines one would be hard pressed to find anything built that doesn't have at least a synthetic blend oil in it now days, most vehicles and equipment come with full synthetic or a blend at minimum from factory anymore.

I am partial to Amsoil myself but opening a discussion about oil is like politics in most arenas, Having been a heavy duty diesel tech for 20+ years I see the benefits of syn over dino as I have used UOA or Used oil analysis and have had many classes on it over the years and see the results of one over the other as well as different brands of oils from the analysis stand point as well.

In short use a 10w30 of your choosing, in a marine application I personally would never use a dino oil.

 

[cwag911]

Keith, just an FYI. I purchased 20w-50 Mobil1 from Amazon. My zero turn mower uses 20w-50  in the transmissions and I wanted to switch to synthetic and that's the only place I could find it. I use synthetic in everything I own.

 

[BigKahuna]

Mercruiser 25W40. The only oil I've ever used and recommended for my I/O....