1989 OMC Cobra 5.7 oil recomendation

Status
Not open for further replies.
D

Donzi

Joined
Apr 30, 2011
Messages
5
Location
Ohio
I am a little confused as to which oil to use in my 1989 OMC Cobra 5.7.
The book calls for straight SAE 30 which I can find.
But I believe this engine has a flat tappet cam setup.
And it is my understanding that newer oils don't have the zinc content that should be used with the flat tappet setup.
I was told to use SAE 30 racing oil but it has been my experience that typical racing oil is intended to be used in short interval applications and really not suited for long term (once a season) usage.
So my questions are what conventional oil would you experts use for my application?
Should I be concerned about the newer oils not being intended for flat tappet cams?
Thanks
 
I have a 1991 5.7 OMC King Cobra. Did the 91 use flat tappets? Because I run Chevron Delo 15/40.

To the OP - Ive had several marine 5.7's and 30w has always caused my low oil psi buzzer to go off after coming off plane. Once I switched to 15/40 - problem solved!
 
Last edited:
How's about using Cam Sheild additive?
Anybody try this stuff?
 
You should be VERY concerned. I know of two fellow boaters who have ruined motors from these new oils.

Check out Amsoils site. They have more than one with appropriate levels of zinc.

I'm not much of an additive fan, better off to simply buy an oil that has the right stuff in it, then you don't have to worry about compatibility and mixing issues, etc.
 
Well it looks like I made the right choice by choosing Delo 15/40 for my 1991 5.7 last year .... it has VOA of 1200ppm of Zinc, which seems to be the opinion on BITOG to be 'more than enough' for flat tappet engines. Score!
 
Myself I'd use Valvoline VR1 30wt dino. It's designed for street use & has everything your 350 needs. Better than their conventional & an additive, IMO.
My .02
 
Yeah I thought about going the VR1 route but I change my oil once a season and VR1 is a short interval oil.
Which means it is low on detergents and is intented for short term use.
 
Originally Posted By: Donzi
Yeah I thought about going the VR1 route but I change my oil once a season and VR1 is a short interval oil.
Which means it is low on detergents and is intented for short term use.

While many race oils are intended for short interval use, VR1 is different and is recommended for street use. It's becoming popular with Harley owners because it can stand up to extreme heat and returns wear numbers lower than many synthetics, with high TBN remaining after 5k miles. Here's a link to a couple of UOA's...

http://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=1967684

Also, if you compare add packs on Valvoline's website, VR1 has more detergents and more zinc & phosphorus than their conventional.

Best of luck with whatever you choose- that's a really sweet setup you have. Friend of mine had a boat with the same powertrain in the early 90's & it would really get up & go...
 
Status
Not open for further replies.

Similar threads

D
Ford FE with roller cam oil?
Replies
13
Views
605
kschachn
L
5.7 hemi oil discussion
Replies
9
Views
869
travis8352
A
What is the right oil to use on a fresh flat tappet engine AFTER break in oil?
2 3
Replies
42
Views
10K
Randy_R
A
1989 Isuzu Trooper oil with high mileage
Replies
11
Views
685
Alexis
D.R.S
5.7 Chevy oil
Replies
10
Views
568
Bear906
Back
Top