longer change interval with synthetic in a 305 SBC v8??

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233
Location
Minnesota
So I just finished putting 5 quarts of walmart 5w-30 synthetic and a cheaper Fram filter in my 91 chevy caprice 5.0L/305 Throttle Body with 152k miles on it in 10 degree weather and -10 windchill thinking "this sucks"... yet what came out after 3200 heavily highway miles on the last dino oil I intend the car to see was pretty dirty looking (I used to be on a strict 2000-2500mi change with dino oil on every car but i'm getting a bit lax because of cold and aggravated physical disabilities the last year) and so I was feeling a little doubtful about things I hear about people going 7500-10k miles and all that. I realize it might well depend on the engine and circumstances and other things so I figured i'd ask the people that would know best. :-P How often should I be changing synthetic on a small block v8? Although this an old and not too valuable car I still like it and hope to drive it for a number of years yet through college and grad school so pinching every possible penny is not the goal, just general frugality. If I have my way i'll have it another 100k miles yet. One reason I went to synthetic and in case it affects things is the wear of starting in the cold (minnesota boy) and that when I drive to school 4x/week it's very close and the car barely has much chance to getwarm. But then once per week I have to drive 250 miles one way for ongoing medical treatment and do 30-45 miles a day of bigcity driving the next few days, so it's a mix.
 
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I'd say 5k. Gen I SBCs are known to shed lots of iron per 1,000 miles (I think some of the dino guys here say 10-15 ppm iron per 1k isn't out of the ordinary) and Doug Hilary's research said 150ppm iron is definitely a condemnation point for any oil. Considering the mileage you've gotten so far, it is probably somewhere in that range. I'd say 5k, 7500 max if you absolutely had to extend it. I'd use Quaker State Ultimate Durability 5W30 since it's only about $3 more than SuperTech, and the VOA looks like it has more antiwear than the ST. JMHO though, either oil is heartier than Chevy could have asked for when your engine was made.
 
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10,004
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Waco, TX
Originally Posted by columnshift
So I just finished putting 5 quarts of walmart 5w-30 synthetic and a cheaper Fram filter in my 91 chevy caprice 5.0L/305 TBI with 152k miles on it in........ How often should I be changing synthetic on a small block v8? Although this an old and not too valuable car I still like it and hope to drive it for a number of years yet through college and grad school so pinching every possible penny is not the goal, just general frugality. If I have my way i'll have it another 100k miles yet.
I would change the oil with the same you just put in once every year. Just add "as needed" along the way Follow that regimen, and the ol' 305 will still last forever (though the timing chain will still need to be replaced at some time)
 
Originally Posted by Dinoburner
I personally would never ever use Quaker State products.
Your choice, your loss. VOA/UOAs show there's absolutely nothing substandard with QSUD, and the price shows it's good for your wallet. Enjoy your Castrol smile
 
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3,646
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Worst Case, Ontario
Originally Posted by Linctex
I would change the oil with the same you just put in once every year. Just add "as needed" along the way Follow that regimen, and the ol' 305 will still last forever (though the timing chain will still need to be replaced at some time)
+1 305 tough as nails. Didn't member Wyrtwister inherit the same car from his parents? He has a 91 Caprice 305 TBI that he has made threads about.
 
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6,415
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Scruffy City
I think with only a few notable exceptions pretty much any oil will do 5K in any car. As long as it is not sludged up inside best you can tell I would run it 5-7500 or 12 months. A 500mile trip once a week should alleviate any condensation form the 4x a week short trips. and if thats consistent you are talking ~ 2200 miles per month so you'll rack up three months is going to put you in that range and you will never see 12 months...
 
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San Rafael, CA
I'll be switching to AMSOIL in my 95 TBI SBC. Probably gonna do 7500mile OCIs for now with a few UOAs. Aiming for 10K mile OCIs. Lots of short trips.
 

columnshift

Thread starter
Messages
233
Location
Minnesota
Originally Posted by DuckRyder
I think with only a few notable exceptions pretty much any oil will do 5K in any car. As long as it is not sludged up inside best you can tell I would run it 5-7500 or 12 months. A 500mile trip once a week should alleviate any condensation form the 4x a week short trips. and if thats consistent you are talking ~ 2200 miles per month so you'll rack up three months is going to put you in that range and you will never see 12 months...
Just to share a followup i'm at 160k now so I think I had 8k on the oil/more than I wanted, but things have been so horrific with our blizzards and such I just couldn't function in the cold. :-P It was darker than I like/I dont think I want to run it that long again, i'm going to aim for 5k for future changes based upon common board recommendations at least from this point onwards.
Originally Posted by Linctex
I would change the oil with the same you just put in once every year. Just add "as needed" along the way Follow that regimen, and the ol' 305 will still last forever (though the timing chain will still need to be replaced at some time)
Well at that rate it would be changed with over 25k on it. :^) It used only about half a quart in 8000 miles... that doesn't seem like much oil usage for an old small block with 160k on it! Maybe my dad (and also my) rigorous 2000-2500mi changes for the car's life kept it in good shape... How long is the timing chain likely to last and will it show signs of needing replacement like increasing noise from getting a bit looser or what? If I get to 260k (another 100k) without having to mess with that i'll probably be happy, if I still have the car after that long i'd be tempted to try my first engine swap and LS it. :-P
 
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6,235
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Kalifornia Kollective
It's not so much about the oil, many will do. It's about the heat in cold weather. There is a fair amount of exposed tin work in an SBC and that can lead to condensation due to temp differentials and the inability to get up to Op Temp and stay there across the engine surfaces. So anything but the 0W-XX synthetics may sludge a bit. If you have a way to block the rad so that it will get up to temp and stay there when driving, you are prolly OK on most any XW-30 or HDEO. But if you do not have good heat control in the engine compartment, just use a good syn 0W-XX of your choosing.
 
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738
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New Hampshire
Like someone else said, I'm running 5,000 mile oci's on everything now, both personally and at work. And we recently stopped carrying conventional oil at work...synthetics across the board.
 
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862
Location
Indy
To follow up on your timing chain question, chances are it could use a timing chain replacement now. The links wear, causing it to get "longer" and sloppier. This will create inaccurate ignition timing since the distributor is driven off the cam. You will likely not hear any noise, and if it jumps time it will just run badly, if at all. It won't hurt the valves, but if you're really worried about it it's not a super hard job. Or just run whatcha brung until it fails. The moral of the story is that most all OHV iron V8's stock timing chain has a shelf life of about 100k-150k miles. But it'll still run.
 
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4,072
Location
Cali
230K on my original 305 in my 83 Silverado, do 3K oil changes, lots of short trips to work which is only 2 miles away, run Pennz dino 10w30 in the winter and 20w50 in the summer with triple digit summers, this has been her life blood since new, also run the STP/FRAM PH 373 2 qt filter just for fun. Cheers2
 
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