Engine Oil - '80-86 305 SBC

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Tynan918

Royal Smart Person
Aug 2, 2021
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I spent $40 on 5 quarts of Lucas Hot Rod Motor Oil, specifically because it had zinc in it...

I can't keep paying that... Is zinc really a must have ?

I've had an '82 Impala, a '78 Impala, and an '86 Monte Carlo... Never had to use zinc specific oil in those engines...

I read and see so many other options...

Factory specs call for 5w-30, I've read others say 10w-30 in the winter and 10w-40 in the summer, some say use cheap oil and add a zinc additive, and I even read some using Rotella 15w-40 diesel oil...

I just don't and can't blow a bunch of money on zinc specific oil, and I'm sure there are cheaper options...

What exactly is zinc used for ?

How does 15w-40 diesel oil work in gasoline engines ?

Can someone explain and recommend something cheaper ?
 
Oct 14, 2008
8,806
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Melville,Saskatchewan
Not sure what caused stuck rings in your engine but I’ve also run rotella in my 76 Malibu with a stock 305, my 2006 suburban with the 8.1, the 70 ss nova with the 450 hp 355 and the Malibu with the 229 v6.
I have a feeling it is the Coop's additive package.
 

ck80

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Supporting Member
Feb 18, 2014
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So, so much more goes into what oil you should and/or can use than just a weight rating.

Years back the Bobistheoilguy website was a good read, but so much info is out of date spec wise with sometimes multiple reformulations you need to really sift these days if you're going to try.

For ME, a good diesel oil was the right call for my older trucks. None have factory cats, either due to build year or having been diesels now sporting gas motors.

I also have low revving motors in the trucks(30-33" tires) mostly chevy 250/292 with only one 350 in the bunch. The 8.1 is a different animal where it doesn't matter so much, but even it is a low revver, even towing. Almost all my time is spent between 700prm to 2400rpm.

But you've got climate to consider thickness, you've got driving habits and setup (Rev level) for shear strength, temps, you've got cat converter type/style, for your zinc/moly/phosphorous contents...

Lots of guys start buying a motor oil and keep buying it, not paying attention to if the standard label changes as a hint at reformulation. Worse still are the ones that walk in and just pick a number of the shelf figuring they're all just about the same.

It's also an interesting read to see what some "experts" have to say about the whole just mixing oils or just dumping additives in thing, and how that effects thermal breakdown, deposits, shear, etc compared to when the materials were part of the actual refining blend.

It's like the argument over what butter/oil spread/lard/etc to cook with,
 
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-dw-

Greasemonkey
Mar 15, 2021
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Just a old half wore out stock 305, use the cheap stuff. Ill be fine. The last 25+ yrs from what Ive seen, more roller lifters gone bad vs flat.
 
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vandyman

Apprentice
Jul 16, 2017
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Most crate motor manufacturers for the GM Gen 1 small blocks will tell you to run 10 - 30. Use a break in additive for flats. And 10 - 30 only after the break in.
 

abbey castro

Royal Smart Person
Oct 31, 2015
1,042
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Harker Hts TX
You spent $8.00 per qt. What is the big deal? What does the GM owners manual say? "An SF/CC quality SAE 5W-30 Energy Conserving oil is the preferred engine oil for your vehicle. I have two toy cars, and two daily drivers. They all get Mobil 1 that cost $8.99 at the Zone. Even my lawn tractor and mower get it. I just stock one oil for all.

Budget limited try the Dollar General nameless oil. It's a 305!
 
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64nailhead

Goat Herder
Dec 1, 2014
5,659
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Upstate NY
You spent $8.00 per qt. What is the big deal? What does the GM owners manual say? "An SF/CC quality SAE 5W-30 Energy Conserving oil is the preferred engine oil for your vehicle. I have two toy cars, and two daily drivers. They all get Mobil 1 that cost $8.99 at the Zone. Even my lawn tractor and mower get it. I just stock one oil for all.

Budget limited try the Dollar General nameless oil. It's a 305!
3 pages of reading, and abbey saved me from typing the same as he did.
 
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Oct 14, 2008
8,806
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They've changed oils so many times now who knows???
Yeah, the CK rated stuff has much less ZDDP than previous versions. Anything to cause less issues with the break down everywhere big trucks.
 

elcotrk

Apprentice
Oct 8, 2021
51
9
8
I spent $40 on 5 quarts of Lucas Hot Rod Motor Oil, specifically because it had zinc in it...

I can't keep paying that... Is zinc really a must have ?

I've had an '82 Impala, a '78 Impala, and an '86 Monte Carlo... Never had to use zinc specific oil in those engines...

I read and see so many other options...

Factory specs call for 5w-30, I've read others say 10w-30 in the winter and 10w-40 in the summer, some say use cheap oil and add a zinc additive, and I even read some using Rotella 15w-40 diesel oil...

I just don't and can't blow a bunch of money on zinc specific oil, and I'm sure there are cheaper options...

What exactly is zinc used for ?

How does 15w-40 diesel oil work in gasoline engines ?

Can someone explain and recommend something cheaper ?
They use Zinc in oil for new
engines and parts replacement like cams for break-in period of 500 miles.
My 1986 Owners manual say 10/30w
 

abbey castro

Royal Smart Person
Oct 31, 2015
1,042
1,303
113
Harker Hts TX
3 pages of reading, and abbey saved me from typing the same as he did.
Gee as if a 305/307 really care what you put in it. Once had a 1976 Laguna S3 with a small block 400. Went 225K on el chepo Havoline straight 20-30w. Got tired of it cause it just wouldn't die. Traded it in for a Ford LTD II Wagon. What a mistake!
 
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