M1 10w40 or Delvac 15w40

[Skier]

I've been running Delvac 1300 15w40 for the last 3 years. Do you think the M1 10w40 HM would be better for my inboard ski boat. It's a 5.7L MPFI engine - Typically 50F-95F outside temp during our ski season. Not unhappy with my oil choice but always wondered if that stuff is too thick at startup. I let the engine warm up 2-3 minutes before we hit the course.

thanks!

 

[fantastic]

I think that would be fine on either & they have rebates for their Delvac in the spring/fall. I'd say the 15w40 is my vote but either one will work.

 

[zrxkawboy]

I agree that either will serve you well.

 

[Skier]

OK, i suppose i will just stick to delvac b/c it's on sale for $14 right now. The prior owner ran M1 15w50 and I stepped down to 15w40 HDEO b/c I thought the 50 was too thick. I've always wondered about the 10w40

 

[alarmguy]

The prior owner ran M1 15w50 and I stepped down to 15w40 HDEO b/c I thought the 50 was too thick.

I’m sorry to hear that but as a second choice 15/40 may be ok

 

[Skier]

I’m sorry to hear that but as a second choice 15/40 may be ok

what would be your 1st choice in a marine application (of the 3 oils I mentioned) ?

 

[Drew7a]

I would run the 15w-40 and not look back.

 

[wpod]

OK, i suppose i will just stick to delvac b/c it's on sale for $14 right now. The prior owner ran M1 15w50 and I stepped down to 15w40 HDEO b/c I thought the 50 was too thick. I've always wondered about the 10w40

Why would 15W-50 be too thick?

 

[BigTimeTA]

I would run Delvac MX for the higher TBN and ZDDP. Also the base oil of MX is thicker and has high density, indicating less VIIs. (There might be other variables affecting the density, but more often than not, oils with higher densities have thicker base oils).

 

[Skier]

Why would 15W-50 be too thick?

Boat is a 2003. The fill cap says 15w40 (b/c they had a deal with Valvoline marine oil). PO ran M1 15w50 for many years. It had a fresh fill of M1 15w50 when i bought the boat in spring of 2017 and I ran it that year.

I was going to stick with M1 15w50 until the manufacturer emailed me put 5w30 Syn in it - I questioned him and then he said stick with heavier oil - i honestly don't think he knew the right answer b/c I have an oddball Chevy LS1 engine. He confused me, so i did way too much reading that year. Decided at the time to go in the middle with 15w40. Ran Valvoline PB in 2018, ran Mobil Delvac 2019-2023 until i ran out of my stash.

it's winter and had some time on my hands to read about oil again - hence my post LOL

 

[kschachn]

No grade is too thick as long as the winter rating is appropriate for your expected starting temperature. For an expensive marine inboard engine I’d use exactly what the manufacturer recommends.

 

[QuadDriver]

Its heresy but I went to the amsoil marine lube many many decades ago when I had an 88 with the 305. My 97 has the injected 350 and same. Its only run warm, I freshwater cool it so I have better heat control and I run the (getting really hard to find) GM depth filters, which I think are now the 1218? used to be pf35 I think.

I dont have an oil loss problem (coolant sure, the ss shim head gaskets all seep after 5 or so years) and I have appx 440 hours on it and spend 99.9% of the time just under 3Krpm