oil weight
 

What type of weight oil should i run a 454 merc 330 horse motor.

Straight 40w

I'm running 30w in my 454mag 365hp is that good or bad? With STP.

You should run a 10w-40 or a 20w-50, or something in that range.

A good Straight 30 or 40 if you run wot a lot.

Never use stp or pennsoil if you have ever taken a motor apart that this $hit was put in you would know why. They are carbon sludge makers.

I was going to say about the same. I hate additives. If the oil was supposed to have it in there, it would already be in it. That is why I use the AMSOIL TRO 20w-50 Racing Oil.

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

shell rotella t - 15/40 best oil period.

Firehawk,

Sorry to go off topic on you, but seems like the oil question got answered. That avitar looks familiar. I took a ride about 20 years ago in a prototype Mustang built by Jack Roush that had that exact same body work and wheels. Was powered by a 351 with GT-40 heads and twin turbos. Same car?

The car in that avatar is a production 1993 Mustang Cobra. They only made that model one year. I think they had about 5 - 10 more hp than a stock GT, and had a different body kit. They still seem to bring big money in good shape. There were some R versions available to race teams only I believe. They were a no air, no power option deal, and they were stripped down for weight.

Unless you boat in cold weather, I would use a straight 40wt or a 15-50 or 20-50. Merc oil is a 25-40w and is now a semi synthetic.

STP and those type of oil additives are nothing more than a polymer with some base stock and maybe a very slight treat of additive.
Adding it to a straight weight oil(30) could bring the viscosity up to a 40 but the polymer that is used in STP is a inexpensive one so ove a short time the polymer will shear and you will have a straight 30 again.
(The oil can shear any less than a straight 30 because straight weights have no polymers.)
Instead of running a straight 30 w/ an additive use a straight 40,(if you want to stay with a straight weight) if not use a good multi-viscosity (20w50 comes to mind) motorcycle oil.

Ken

Ahhhh...that's right...forgot they were building Cobra's that early. The body kit was cool. Too bad the Roush motor never made it to production! It was over 400hp. Not hugely impressive by today's standards but in 1988 it was crazy horsepower! Now....back to your regularly scheduled oil programming! :cool-smiley-011:

NEVER, EVER use 10w40 in ANYTHING GM powered. :hitfan:

That particular multi weight oil breaks down faster than anything else. Mercury recommends straight 40w, 25w-40, or 20w50, if I'm memory serves me correctly.

Read here: http://www.mercurymarine.com/service...qs/fueloil.php
This thread contains some interesting reading too: http://www.boatengine.net/t/055289.html

I'm a big fan of synthetic oils, but that's not what we're talking about.

Tell me the difference between a 20w-40 and a 10w-40? Just curious...

A 10w oil starts out as a base 10 weight oil, and a 20w oil starts out as a base 20 weight oil, put simply. The polymers that are used to create the '40' in the 10w40 oils breaks down faster that those used in the 20w40 oils. Oil chemistry is very complicated, and I won't pretend to be an expert. OilDoc does a good job of explaining oils in this thread: http://www.boatengine.net/t/055289.html

Thanks i think ill go with 20w40. the avatar is actually a picture of a car like mine i just sold. Jayhawk explained exactly what it is. They did come out with gt-40 heads stock. with a blower and exhaust they are a 400 horse at the rear wheel car.

Royal Puple straight 40 weight

Weights that would work for you in my opinion:

30wt (if ambient temps at or around 40*F)
40wt (RP;Kendall; Castrol; Penzoil etc)
25W-40 (Mercury Semi-syn)
15W-40 (Amsoil Marine); Rotella;DelVac
15W-50 (Mobil-1) Silver Cap
20W-50 Mobil-1 V-Twin; Amsoil; RP; Redline; Castrol; Kendall etc.)

My choice for your engine:

Mobil-1 SilverCap 15W-50

$24.00/5 qt @WallyLand

Why? A lot of boaters on this board use it and tear down looks real good.

Mobil-1 V-twin 20W-50 if you can go $9/qt or Redline 20W-50 have the highest levels of anti wear additives I have seen so far.