What should I be using in a '83 SBC?

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So the Grand Prix is finally registered, insured, and back on the road I swear the DMV works better in a pandemic than it does normally ??? It's an '83 305 SBC, with a CCC Quadrajet, still has that stupid factory dual bed pellet converter Made in Canada I believe, there's a maple leaf stamped on the manifold Canada Most importantly, it's on the factory flat tappet cam that I've heard have a reputation of being soft and wearing down Dad's been using off the shelf 5w/10w-30, before I knew about the lack of zinc and ZDDP, OTOH it hasn't gone 1k since 1988 I've since added a bottle of this Rislone stuff every oil change [Linked Image from images-na.ssl-images-amazon.com] Is there an oil off the shelf that'd be better suited to this old beast?

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michaelluscher

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Originally Posted by bullwinkle
Rotella T5 10W30 seems to do pretty well in these. It's possible to flatten cams in those, I had an '85 Chevy G20 van that ate one on a 305.
Diesel rated oil in a gas engine? I didn't know you could do that shrug Should I still add a zinc additive, or it's good out of the bottle? I saw they've got a "Multi Vehicle" T6 that's both CK4 and SN rated, but that's kinda thin 5W-30 They've got T6 5W-40 in good value 2.5 gallon bottles for a fair price, would that do it?
 
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Originally Posted by michaelluscher
Originally Posted by bullwinkle
Rotella T5 10W30 seems to do pretty well in these. It's possible to flatten cams in those, I had an '85 Chevy G20 van that ate one on a 305.
Diesel rated oil in a gas engine? I didn't know you could do that shrug Should I still add a zinc additive, or it's good out of the bottle? I saw they've got a "Multi Vehicle" T6 that's both CK4 and SN rated, but that's kinda thin 5W-30 They've got T6 5W-40 in good value 2.5 gallon bottles for a fair price, would that do it?
Ive seen theories that too much ZDDP can have a negative effect due to making the oil acidic.. but that was a long time ago. Diesel rated oil in a gas engine? Sure. The big 'fear' is that the ZDDP will harm cats (if it has a S rating it will have lower ZDDP?) ... but you are pouring zddp in so you are basically brewing HDEO. That SAE chart looks like a newer spec than your 83. GM didnt spec 5w30 until 1986? The API rating in 1983 was SF and is now obsolete due to formation of sludge. I have also seen theories that once the cam is broken in that the need for ZDDP is much less. Once the cam is hardened zddp does nothing additionally? So with all that being said i would probably just stick with VR1 or T4 T5 or T6 an 83 305 is pretty mild.
 
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In my opinion, the best oil would be a full saps Euro oil like a 0W40. Has plenty of zinc being full saps and will provide faster lubrication to the valve train than a 5 or 10W30. No additive is needed with such an oil. Nice car!
 

SR5

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Originally Posted by michaelluscher
Diesel rated oil in a gas engine? I didn't know you could do that shrug Should I still add a zinc additive, or it's good out of the bottle? I saw they've got a "Multi Vehicle" T6 that's both CK4 and SN rated, but that's kinda thin 5W-30 They've got T6 5W-40 in good value 2.5 gallon bottles for a fair price, would that do it?
Yes, they use to be sold as mixed-fleet HDEOs, mixed as in suitable for both Gas (petrol) and Diesel engines. Less sold as this now days, due to exhaust cat concerns on modern cars, but they still work well for both engines, especially older gas cars and HDEOs are often used in motorcycles too. In fact Rotella T6 5W40 is rated " JASO MA/ MA2" which is for motorcycles, which are regular gas engines. (T6 5W40 PDF) Good out of the bottle, nothing to add. Here is a link to a recent T6 5W40 VOA, it shows a healthy 1035 ppm zinc. https://www.bobistheoilguy.com/forums/ubbthreads.php/topics/5253264/
 
It's interesting how those oil recommendations are graduated by the low temp requirement and the xW number moves up with the temp. Really can't argue too much with that considering the oil was not nearly as good as it is 37 years later. The wide range of grades on the upper end indicates to me that GM didn't care what you ran.
 
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Hmm.........I have a 305 LU5 crossfire in my 82 T/A KITT with 85K original miles and he's been enjoying M1 HM 10W40 and the exact zinc additive pictured above. I'm keeping a eye on this one popcorn popcorn2 Dave
 
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I'm surprised they recommended 10w40-- GM cars of mine from that era come with a specific prohibition. +2 on the rotella 10w30. Will you be putting in a modern, generic honeycomb cat? They're only ~$50 or so and your old one might be worth $$$ at the scrap yard.
 
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I'm not sure GM had cam problems in '83. I think that came later. The stock 305 has very mild cam lift and valve spring pressures (extra Zn not required - 600ppm plenty). GM definitely forbid 10w-40 at that time but 10w-40 has greatly improved since then. I'd be using 10w-30 and probably SuperTech Syn.
 
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Originally Posted by ka9mnx
I'm not sure GM had cam problems in '83. I think that came later. The stock 305 has very mild cam lift and valve spring pressures (extra Zn not required - 600ppm plenty). GM definitely forbid 10w-40 at that time but 10w-40 has greatly improved since then. I'd be using 10w-30 and probably SuperTech Syn.
Years ago before my time on BITOG I called Mobil CS and they were NUTS and recommend 15W40 for my trans am ?? Dave shrug
 
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For a stock (mild) cam, a decent 10w30 oil should be fine. Increased valve spring pressures need increased ZDDP. Racing oils may not have the detergents needed in street driven cars.
 
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I thought soft cams were a problem in the 70's on the 305's. After that they came with pre-flattened lobes. LOL Pretty sure those bad cams weren't helped by anything? As in, it was a hardening problem and they were going to go flat anyhow. Low lift and low spring pressure, those cams were going to go bad no matter what. Almost a shame. Seems like a classic car to do a quick cam and induction swap on. Oh dreams of my youth... Mild RV cam and maybe a 4bbl, keep the dead smooth idle but otherwise wake up that mill.
 
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As long as that 305 is stock, any HDEO will be fine, but so would any good name brand marine oil like Quicksilver from Mercury. Bazzillions of boats out there with flat tappet cams. You could go looking for a specific oil, but why ... Use what you can get locally at a good price. Change at 3~5K miles and put in a good filter. If using ZDDP additive, go by additive ratio from MFG. Most are 1 oz per quart of oil. Too much is far worse than to little (acidifies oil).
 
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Those cams are super mild. No need for more zinc than what regular 10w30 has in it. There are thousands and thousands of flat tappet camshafts running right now, as you read this, without any kind of special oil and they haven't turned into broom sticks.
 
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Originally Posted by michaelluscher
Originally Posted by bullwinkle
Rotella T5 10W30 seems to do pretty well in these. It's possible to flatten cams in those, I had an '85 Chevy G20 van that ate one on a 305.
Diesel rated oil in a gas engine? I didn't know you could do that shrug Should I still add a zinc additive, or it's good out of the bottle? I saw they've got a "Multi Vehicle" T6 that's both CK4 and SN rated, but that's kinda thin 5W-30 They've got T6 5W-40 in good value 2.5 gallon bottles for a fair price, would that do it?
T6 would be good too-check Brickseek for local Wal-Marts carrying it for $15/2.5 gallon jug, that would work too. People add ZDDP to it too, but I'm not sure a 305 would have an aggressive enough cam to need it. T5 (&T6) were dual gas/diesel rated until recent (SN rating) times.
 
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