just re built twin 350 mags stroked 383cubes 420 hp i broke in with straight 30
know what should i run. this is cold ocean water in newengland.

Simple...Im sure everyone will agree with me here. Mobil 1 15w50

Randy
"Bad-Habit"

Here is some interesting info I found on a website from an admitted oil 'geek'
maybe you can sort it out.

http://home.earthlink.net/~wotmotors...riteoils-2.htm

I run straight 40 wt oil in everything.

Mobil 1 15w50 is what is recommended by many of the local engine builders here in Louisiana.

In studying this and all the Amsoil products test results; Mobil-1 15w 50 performs about the same or better than most everything when you evaluate Viscosity Index tests which relate to an oils ability to protect the engine bearings best and High Temperature High Shear tests which is a measure of the oils ability to hold viscosity under high temps, except the VERY BEST Amsoil Racing Severe Duty TRO Series 2000 20w50 that Merc supposedly uses in it's 1050's. Redline is as good in shear but not quite as good in high temps. RP was not looked at. I wonder about the molybedium sulfate in it and how condensation plus the sulfate could form acids and most manufacturers specifically say not to use this additive or graphite is why there is not much info about it anywhere. I would still like more info on this. I know racers use it a lot but they change oil after every run. Even API SL conventials have sulfur in them still. So condensation is not a big of concern in Grade 4 or Grade 5 derived synthetics from an acid formation standpoint which is a huge potential advantage. Mobil-1 15w 50 is grade 4 derived and definately a fully synthetic oil.

So Mobil-1 15w50 from Walmat in bulk is about $ 4.00/qt and i talked to a rep at Sterling who said they go with Mobil-1 15w50.

Amsoil Racing TRO Series 2000 20w50 including shipping and handling is about $ 8.75/qt That is what merc supposedly uses in it's 1050's as it holds up to heat best of all synthetics tested.

Amsoil 2000 Severe Service 20w50 ought be better for more than twice the price of Mobil-1 15w50. It has a base that is >12 so it's from Grade 5 base which turbine engines in commercial airplanes use I understand.

I also read on a site about a fellow who opened an oil filter with and without a magnetic jacket and said you could see metallic material on the sides of the filter with a jacket.

And as always use what you want! I am an oil geek I guess.

I'd run 15w-40 Rotella,
25w-40 Merc,
Amsoil 10w-40 synthetic,
Mobil1 or Rotella synthetic 5w-40.

I see no reason to run a 50wt oil in that motor, even in tropical water... Won't hurt it though. Your call.

Well certainly I must agree with you in that you are right you don't need a 50 wt but it will work fine. The "cold pour" on 15w-50 Mobil-1 is good to down to -65 degrees F so it covers extremes at both ends. It's a great value in a synthetic. Amsoil 15w 40 Marine is another good choice at grade 4/5. I agree that Rotella 15w40 and 25w40 Merc are great conventionals and also realize there are several "straight weight" folks here either 30 or 40 and that was/is still a respected choice. Amsoil 10w40 Series 2000 covers the bases well and is a Grade 4/5 derived oil.

The only point it that 15w50 Mobil-1 at $ 4.00/qt in 5 qt containers is a value at Walmarts as Rotella and Merc are around $ 3/qt but very good conventionals. So price is not such a big factor anymore here, as I think it was a determining factor for many thinking about going synthetic previously.

The very best is the Severe Duty 20w50 Amsoil 2000 at nearly $ 9.00/qt. I would use it if I had a big expensive blower motor or was running really hard or have the extra money and want the absolute best. If you had a 10qt pan it could run about a hundred an engine per change and I wouldn't go past the recommended intervals. But if you have 60-80k into an engine it's all relative.

Who sells those filter magnets again?