1985 suburban mark iv 454 build. What oil do you guys like?

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Mar 30, 2025
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Howdy all,

We recently rebuilt a barn find 1985 c20 suburban. It was an 80k mile truck and we pulled it to clean up the motor. Like most builds, we got deeper and deeper but I tried to stay pretty conservative. We bored it .030 over to 461 and lightly polished the factory crank, reused the factory rods and replaced all bearings throughout with standard king brand bearings. Cam wise we converted to a Howard’s hydraulic roller setup with crane 1.7 gold rockers. Head wise we went with AFR 265 oval port 109cc, and small -10.00 cc domes. Intake is an edelbrock air gap rpm to a Holley sniper 2.

The engine runs insanely well and I’ve put around 2300 miles on it. We broke it in with Driven 5w-30 break in oil for 800 miles and then switched over to Driven GP1 10w30 per their recommendation. Our oil pressure is awesome but I’m eating about 1 quart for every 1000 miles. I did read that these old big blocks can sometimes do that.

Now to the main question. Am I using the right oil? Is this oil overkill or should I swap to something cheaper, different, etc?

IMG_7052.webp
 
Old big-block Chevies are known to consume oil, but with a proper rebuild it shouldn’t be that high, I don’t think?
Did you use a ‘performance’ type of piston ring that allows for consumption?
Obviously follow the builder’s recommendation; have you asked them what they think of the consumption?
The ‘wisdom’ on old BBC’s is they ‘like’ thick oil; even new HP ones recommend 50-weight oil I think. A run of VR 20W-50 might be in order to see what it does.
BTW, really nice clean truck; I like the ‘stealth’ beige colour!
 
Old big-block Chevies are known to consume oil, but with a proper rebuild it shouldn’t be that high, I don’t think?
Did you use a ‘performance’ type of piston ring that allows for consumption?
Obviously follow the builder’s recommendation; have you asked them what they think of the consumption?
The ‘wisdom’ on old BBC’s is they ‘like’ thick oil; even new HP ones recommend 50-weight oil I think. A run of VR 20W-50 might be in order to see what it does.
BTW, really nice clean truck; I like the ‘stealth’ beige colour!
Thanks! It’s the factory paint! The interior was like a time capsule too! I wonder if I should bump it up to a 15/40 driven gp1 instead? Some things I’ve read say don’t use synthetic in these old engines because it’s too slick and will get past seals. Should I switch to conventional instead (Valvoline VR1)?

I went with these moly and steel piston rings for the build:

https://www.summitracing.com/parts/SLP-E-233K30

Original pics of the truck when we bought it:

IMG_7084.webp


IMG_7082.webp


IMG_7065.webp
 
For that engine, a break in on conventional oil, with plenty of short full throttle pulls for ring seating. It's not as easy to seat rings on rebuilt engines. As much as we would love to think the dimensions are perfectly stable, they are not always so.

After break in, I'd go right to M1, 15W-50. Those are big heavy pistons and rods, are slinging around on 2.2 inch bearings. Both Ford and Chrysler use bearings up to 2.5 inches to handle those high loads and heavy pistons.

EDIT: Very cool looking truck and I love the wheels!
 
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For that engine, a break in on conventional oil, with plenty of short full throttle pulls for ring seating. It's not as easy to seat rings on rebuilt engines. As much as we would love to think the dimensions are perfectly stable, they are not always so.

After break in, I'd go right to M1, 15W-50.
Thanks, I would think these rings are seated by now (maybe not!)? There is zero smoke anytime anywhere.

IMG_7069.webp
 
I'm guessing by the trees with full foliage you are in a warmer climate, so I would suggest a cheaper option of 15W-40 diesel oil of any brand.

Otherwise, I second Cujet with the M1 15W-50.
 
interesting question, Mobil 1 will be the only answer here of course, though other brands will be good also or even better,. try a 5w-40 full synthetic.
 
Thanks all. One more thing to note. This engine doesn’t see north of 5300 rpm and I tow with it once a month 100-200 miles (9k trailer).
 
Nice ride and well done on that BB. Good choices on parts; I might have used a smaller cam. Perhaps try a little heavier oil, but 10w30 should be fine. Good luck and enjoy that 'burbon!
 
Howdy all,

We recently rebuilt a barn find 1985 c20 suburban. It was an 80k mile truck and we pulled it to clean up the motor. Like most builds, we got deeper and deeper but I tried to stay pretty conservative. We bored it .030 over to 461 and lightly polished the factory crank, reused the factory rods and replaced all bearings throughout with standard king brand bearings. Cam wise we converted to a Howard’s hydraulic roller setup with crane 1.7 gold rockers. Head wise we went with AFR 265 oval port 109cc, and small -10.00 cc domes. Intake is an edelbrock air gap rpm to a Holley sniper 2.

The engine runs insanely well and I’ve put around 2300 miles on it. We broke it in with Driven 5w-30 break in oil for 800 miles and then switched over to Driven GP1 10w30 per their recommendation. Our oil pressure is awesome but I’m eating about 1 quart for every 1000 miles. I did read that these old big blocks can sometimes do that.

Now to the main question. Am I using the right oil? Is this oil overkill or should I swap to something cheaper, different, etc?

Just stick with a Dino oil and see if the consumption tapers off. I’d use VR1 20w50 for now. No sense feeding premium synthetic to an engine burning that much oil.
 
Nice ride and well done on that BB. Good choices on parts; I might have used a smaller cam. Perhaps try a little heavier oil, but 10w30 should be fine. Good luck and enjoy that 'burbon!
Thanks! The cam is pretty small:

Valve Lift Intake:
 .510
Valve Lift Exhaust:
 .538
Duration Intake:
 266
Duration Exhaust:
 274
Duration at 050 Intake:
 213
Duration at 050 Exhaust:
 221
Lobe Separation:
 112
 
Just stick with a Dino oil and see if the consumption tapers off. I’d use VR1 20w50 for now. No sense feeding premium synthetic to an engine burning that much oil.
I wonder if I just slowly start adding this to the existing mix of 10w30 driven?
 
Thanks! The cam is pretty small:

Valve Lift Intake:
 .510
Valve Lift Exhaust:
 .538
Duration Intake:
 266
Duration Exhaust:
 274
Duration at 050 Intake:
 213
Duration at 050 Exhaust:
 221
Lobe Separation:
 112
BB's love roller valve trains! Great choice. My comment was more about the usable RPM range of your Suburbon.
You do have a lotta cubes; that thing must be a stump puller. That cam would be perfect in my '68 L36 Vette. I might never get outta 2nd gear...
 
BB's love roller valve trains! Great choice. My comment was more about the usable RPM range of your Suburbon.
You do have a lotta cubes; that thing must be a stump puller. That cam would be perfect in my '68 L36 Vette. I might never get outta 2nd gear...
Thanks! Since we built it for towing, the cam’s power band is 1200-5000 rpm.
 
Howdy all,

We recently rebuilt a barn find 1985 c20 suburban. It was an 80k mile truck and we pulled it to clean up the motor. Like most builds, we got deeper and deeper but I tried to stay pretty conservative. We bored it .030 over to 461 and lightly polished the factory crank, reused the factory rods and replaced all bearings throughout with standard king brand bearings. Cam wise we converted to a Howard’s hydraulic roller setup with crane 1.7 gold rockers. Head wise we went with AFR 265 oval port 109cc, and small -10.00 cc domes. Intake is an edelbrock air gap rpm to a Holley sniper 2.

The engine runs insanely well and I’ve put around 2300 miles on it. We broke it in with Driven 5w-30 break in oil for 800 miles and then switched over to Driven GP1 10w30 per their recommendation. Our oil pressure is awesome but I’m eating about 1 quart for every 1000 miles. I did read that these old big blocks can sometimes do that.

Now to the main question. Am I using the right oil? Is this oil overkill or should I swap to something cheaper, different, etc?

View attachment 270936
Good looking rig!
 
Were the heads rebuilt checking valve guides, spring retainer to valve guide boss clearance (retainer crushing seal) type of valve seals, and proper pushrod length (valve to rocker contact)? Also was the block deck and/or heads milled? If intake isn’t seated properly, (due to heads milled) oil can be drawn in between intake gasket and intake port on head. Does your valve covers have a baffle for the PCV valve? If not, a lot of oil can be drawn through the PCV valve. As some have mentioned, 10W30 isn’t going to cut it for a big block Chevy. 20w50 (VR-1) would be a great oil.
 
Were the heads rebuilt checking valve guides, spring retainer to valve guide boss clearance (retainer crushing seal) type of valve seals, and proper pushrod length (valve to rocker contact)? Also was the block deck and/or heads milled? If intake isn’t seated properly, (due to heads milled) oil can be drawn in between intake gasket and intake port on head. Does your valve covers have a baffle for the PCV valve? If not, a lot of oil can be drawn through the PCV valve. As some have mentioned, 10W30 isn’t going to cut it for a big block Chevy. 20w50 (VR-1) would be a great oil.
Thanks! We put on a set of new AFR aluminum heads and definitely measured for push rod length. We have a Wagner Pcv system set through a catch can.
 
Thanks! We put on a set of new AFR aluminum heads and definitely measured for push rod length. We have a Wagner Pcv system set through a catch can.
Nice evac system. Still, needs a PCV baffle. How much oil are you finding in the catch can?
 
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