Mobil 1 Synthetic 10w-40 or 15w-50

[celdred]

Hey gang, sorry to bring this up again and yes, I have searched and read many threads regarding oil on this site.

It comes down to this...I bought my first Malibu late last fall and when it came time to winterize I went with Mobil 1 synthetic. They don't offer 15w-40 so I used 15w-50 as I don't get started to early in the spring or run late into fall. Also, the boat is 10 years old with 550 hours.

Anyway, it's that time of year again and I'm wondering your thoughts on using the 15w-50? Or should I go with 10w-40? For what it's worth the engine ran great all season and did seem a bit quieter but that could just be in my head.

I was thinking of just using Rotella or Chev Delo 400 15w-40 but my buddy says I shouldn't now that I made the switch to synthetic.

[cwkoch]

Amsoil makes a 15W-40 oil, they even call it a Diesel and Marine oil. I run it. It's great.

http://www.amsoil.com/storefront/ame.aspx

If you want to stick with Mobil 1, I'd probably go with the thinner oil. You're still getting plenty of protection with it, and possibly better fuel economy.

[eyepeeler]

[billb]

I know someone who has switched back from synthetic to mineral (regular) oil. No problems (yet). Just one season under his belt after the switch back, though.

[Bobby Light]

You can go back and forth between oils if you want, it's a myth that it will harm your engine. I didn't think Mobile was making 15/50 anymore, I thought they went to 5/50.

[Woodski]

When you have success with something, there is good reason to stick with that. A small block GM V8 will operate just fine on the lighter viscosity oil, I actually use 5W-30 or 10W-30 synthetic. Since boats tend not to operate in very cold weather, you really don't need to go with the lighter side oil (first number)for start up conditions. The second number signifies the operating viscosity and really anything from 30 on up will be fine. You certainly don't need to go to 50 weight, but if the quieter aspect is something you like, it certainly is okay. There will be a slight efficiency penalty you will pay (performance and fuel economy) but you will probably not notice it in normal conditions. One caveat, the Hammerhead needs the thicker oils (50W) as they are built with looser tolerances. Aso, 550 hours is not a lot of hours on a boat engine assuming normal operating conditions.

Edited September 18, 2010 by Woodski

[celdred]

Thanks everyone! Just drained my oil after a full season in VT and it looked great so I'm going to stick with synthetic. Since 15w-50 is much harder to fine and it seems most feel 10w-40 will suffice I'm going with that. Nice thing is Wally World sells 5 qt jugs for like $25 and since the engine was spec'd to use 40 weight that's what I should use. I'll see if I notice any difference (engine noise, performance, fuel economy) next year.

I guess it's more important that the viscosity at running temps (40) be adhered to than the viscosity at startup (10) in my case rather than the recommended (15).

Sad to be winterizing today but groin injury cut my season short. Oh well, we'll get an early start next spring and the lighter oil will surely help with that. -c

[rodman]

I wounder how they spec the oil for our boat motors. We never run them in below zero so why the 5,10,15'S, weights and we never get over 170 degrees (bar any issues)so the 40 will be fine.

Heat and Heat only breaks down oil we never have that issue. Most of our cars run normal over 210.

[Chia]

Thanks everyone! Just drained my oil after a full season in VT and it looked great so I'm going to stick with synthetic. Since 15w-50 is much harder to fine and it seems most feel 10w-40 will suffice I'm going with that. Nice thing is Wally World sells 5 qt jugs for like $25 and since the engine was spec'd to use 40 weight that's what I should use. I'll see if I notice any difference (engine noise, performance, fuel economy) next year.

I guess it's more important that the viscosity at running temps (40) be adhered to than the viscosity at startup (10) in my case rather than the recommended (15).

Sad to be winterizing today but groin injury cut my season short. Oh well, we'll get an early start next spring and the lighter oil will surely help with that. -c

Just make sure your oil meets the API standards recommended by Indmar!

Note the "CAUTION" box:

the use of engine oil other than 15W-40 with an API SJ/CG4 designation can cause engine damage.

Edited September 19, 2010 by Cervelo

[skier_88]

I typically use RotellaT in all of my cars. Thats what my Dad shop uses so thats what I use. He uses straight 30W in his boat. The PO with my boat has always used Mobile 1 synthetic, so I'll use the same. Not sure how much differene a synthetic oil will make, if any, in a boat since we typically change every 50 anyway. I'll just maintain the consistency of the boat.

[celdred]

You guys are putting me more at ease every post. Basically I don't understand Indmar's cold weather viscosity rating either as we use our boats in summer (at least i do) and oil temp guage never goes above 160. For what it's worth, today at Wal-Mart I picked up the 5 qt jug of Mobil 1 synthetic 10w-40 for $23. Wouldn't you know it, the Shell Rottella T 15w-40 that many on this site recommend was prominently displayed on the end of the oil isle for $12 a gallon. For kicks, I compared the API rating and the Rottella was actually rated SM while the Mobil 1 was rated SL (one step down SL).

I think the SM rating is rather new and I'm not sure who assigns the ratings (gov't agency? manufacturer?) but either way they both exceed Indmar's SJ recomendation. In the end I bet the Rottella would be just fine but my BU is my baby so I splurged the extra $7....

On a side note, weather looks good this week and Oil change is as far as I got winterizing today. Anybody have any thoughts on the effects of heading back out for another day on the water and then leaving that just slightly used oil in over the winter?

[MalibuNation]

Ideally you would want the engine stored over the winter with as clean as possible oil ... none of that dirty acidic old oil. To answer your question about using your boat one more time, you'll be fine and don't worry.

I contacted Indmar and they said 15w-50 Mobil One was fine.

[celdred]

I contacted Indmar and they said 15w-50 Mobil One was fine.

Great! BTW -looked at API rating on Mobil 1 quart bottles at Bond Auto this morning and they say SM. Probably just old stock at Wal-Mart.

Also, for any of you guys with Bond Auto nearby they are closing out Mobil 1 oil filters. I picked up three M1-302's for $6 each.

[NE4now]

Sorry to stir up an old topic but I came across this thread while searching for info about winterizing/maintaining a 1999 Malibu Sportster I just purchased.  The oil recommended in the manual is Penzoil Marine 15w40 which is no longer available and I prefer to use fully synthetics in all my engines anyways.  My friend works in a Marina and says they use/offer Rotella T6 15w40 Fully Synthetic in all the inboards.

According to email from Indmar, for the 5.7 engines:

Mobil1 15w50 - "Would be a good choice for fully synthetic" and is what he recommended initially. 

Rotella T6 Fully Synthetic 15w40 -  "Would be fine as well even though it says it is for diesel, it meets our requirements." 

 

Thanks for all the insight & information on this forum.  Hopefully it will help me keep this boat a great source of pleasure for my family for a long time.  It is 20+ years old but has under 500 hours and appears extremely well maintained.

[Eagleboy99]

15-40 has been in mine since day one.  Was Pennzoil and now diesel rated Shell dino juice.  I see no need to use syn or semi-syn.

[SkiPablo]

On 10/19/2019 at 11:57 AM, NE4now said:

Sorry to stir up an old topic but I came across this thread while searching for info about winterizing/maintaining a 1999 Malibu Sportster I just purchased.  The oil recommended in the manual is Penzoil Marine 15w40 which is no longer available and I prefer to use fully synthetics in all my engines anyways.  My friend works in a Marina and says they use/offer Rotella T6 15w40 Fully Synthetic in all the inboards.

According to email from Indmar, for the 5.7 engines:

Mobil1 15w50 - "Would be a good choice for fully synthetic" and is what he recommended initially. 

Rotella T6 Fully Synthetic 15w40 -  "Would be fine as well even though it says it is for diesel, it meets our requirements." 

 

Thanks for all the insight & information on this forum.  Hopefully it will help me keep this boat a great source of pleasure for my family for a long time.  It is 20+ years old but has under 500 hours and appears extremely well maintained.

 

The Rotella 15w40 will be fine b/c you don't have Cats on that engine.   

[Nitrousbird]

I run Mobil One 10W40 in mine.  

Some of these other recommendations don't take into account the low COST of this oil vs what you get.  Wally World carries it pretty much all the time for $22 for 5 quarts of full synthetic.  Sure, you can get Amsoil - which is better - but far more expensive.  Or save a couple dollars with a Rotella dino oil (or pay even less on Mobil Delvac).  But Mobil One at $22 for 5 quarts is pretty much the best performance value in oil you can get.  I run it in everything, including my lawn mower.

[williemon]

I like running a 15 40 diesel oil. Delvac, shell, whichever I find. The temp range you run it pretty much dictates what you can use as long as the other markers like sj are met or exceeded. For my cars, 6 over the years, I run 5 30 Dino oil and have over the past 30 years got over 200k on all of them without any oil related issues prior to selling. 

[NE4now]

On 10/21/2019 at 11:12 PM, Nitrousbird said:

I run Mobil One 10W40 in mine.  

Some of these other recommendations don't take into account the low COST of this oil vs what you get.  Wally World carries it pretty much all the time for $22 for 5 quarts of full synthetic.  Sure, you can get Amsoil - which is better - but far more expensive.  Or save a couple dollars with a Rotella dino oil (or pay even less on Mobil Delvac).  But Mobil One at $22 for 5 quarts is pretty much the best performance value in oil you can get.  I run it in everything, including my lawn mower.

Pretty much same here (Synthetic in everything and usually mobil1). I ended up grabbing the 15w50 Mobil1 on sale with a M1 filter for less than $35 and got a $5 off coupon for next time. Definitely not complaining.