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#4672841 - 02/21/18 08:51 AM 73 Corvette with unknown oil mileage report
Hawkfanatic Offline


Registered: 11/30/10
Posts: 10
Loc: Northern KY
Hello everyone, I need some interpretation on the oil report below.

This is a 73 Corvette that my uncle is considering buying. No one knows how many miles are actually on the oil, so I guessed at 1000. It could be as little as 500, it could be as many as 10,000. I have no way to know. I also do not know the brand or viscosity.

I know the oil was black when I pulled it. The car was warm, but had sat for about 30min, and that I sampled the first oil that came out of the drain. I basically just loosened the plug and let it dribble out.

I am curious if these numbers seem worse if there is only 1,000 miles on the oil than if there were 10,000 miles on the oil?

Thanks everyone.

_________________________
2006 Toyota Tundra Double Cab TRD 4x4
1999 Pontiac Trans Am Firehawk
1991 Pontiac Firebird Formula

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#4672891 - 02/21/18 09:18 AM Re: 73 Corvette with unknown oil mileage report [Re: Hawkfanatic]
CourierDriver Offline


Registered: 12/27/09
Posts: 4826
Loc: Tn.
I'll take one

https://images.search.yahoo.com/search/images;_ylt=A2KLfSK9jI1aWhEAONxXNyoA;_ylu=X3oDMTByMjB0aG5zBGNvbG8DYmYxBHBvcwMxBHZ0aWQDBHNlYwNzYw--?p=73+corvette&fr=dss_yset_chr
_________________________
Appreciate America, no one is migrating to Mexico, the Middle East,Russia,and so on,,they are all coming here...remember ??

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#4672898 - 02/21/18 09:22 AM Re: 73 Corvette with unknown oil mileage report [Re: Hawkfanatic]
69GTX Offline


Registered: 09/23/15
Posts: 3742
Loc: Connecticut
Too bad they didn't do a TBN on the oil. That would have been a good marker of very old/tired oil vs. something only 1K-5K miles old.

Judging from the low calcium, moderate magnesium, phos/zinc, moly/boron mix, it resembles a 5w-30 Mobil 1 oil. If so it started out life around 11.1 viscosity. So that could mean a fairly used up oil to drop from 11 to 9.67. Certainly not 1K miles. Maybe 4K-8K? I don't think this is 1K mile oil as everything seems to point towards it being a Mobil 1 - 30 grade.

PQIA

Isn't this a flat tappet engine? And if that's the case, you'd want more zinc in there than M1 5w-30 could provide. Some Castrol oils also have higher magnesium though this doesn't look like one of them with that low a Calcium number and lower viscosity.
_________________________
----------------

2002 Lincoln Cont 4.6L DOHC/ 81K mi /PPlat 5w30/FUG XG2
1999 Camaro SS M6 /19K /Mobil 1 0w40 /Fram UG /GM MTL-ATF
1969 Ply GTX/RRs

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#4672928 - 02/21/18 09:45 AM Re: 73 Corvette with unknown oil mileage report [Re: Hawkfanatic]
BrocLuno Offline


Registered: 09/06/15
Posts: 5240
Loc: Kalifornia Kollective
OK, uncle buys Corvette. How many actual miles are on the chassis and engine? Auto or stick? What does the tranny fluid and power steering fluid look like? A lot of corrosion around the battery terminals? Is the rear end full?

Look critically at the whole, not just the oil.

Pull a valve cover. That will tell you more about the engine than a unknown mileage oil sample.
_________________________
Formerly in marine engineering. In an earlier life I owned my own petroleum tank truck, and hauled for the majors and independent's.

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#4672988 - 02/21/18 10:13 AM Re: 73 Corvette with unknown oil mileage report [Re: Hawkfanatic]
JohnnyJohnson Offline


Registered: 10/22/09
Posts: 2394
Loc: Wet side WA
Perhaps the worst UOA I have ever seen on BITOG.
_________________________
2004 Toyota Corolla 119727
Out: QSUD 5W-30 Purolator One 5030
In: Valvoline ML 5w-30 TG4967 117530 2-8-18
2006 Duramax 73752
Out: T6 5W-40 M1-303
In: T6 5W-40 XG9100 73752 4-22-18

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#4673016 - 02/21/18 10:27 AM Re: 73 Corvette with unknown oil mileage report [Re: Hawkfanatic]
zeng Offline


Registered: 09/01/15
Posts: 2095
Loc: Malaysia
Presence of Mo, Boron , Ca and Mg indicates it's a Mobil 1.
High metal wear rates of Fe, Cu, Pb etc indicates excessive long OCI of 15000-25000 miles of several years leading to extensive oil oxidation and viscosity thickening to 9.67 cSt [email protected]*C.
Thus, oil grade was likely a xW20 of virgin [email protected]*C of 8.5-8.8 cSt.

Suggest 2 short OCI's of 5000 miles each with a mineral/blend xW30 for cleaning, follow by any full synthetic xW20 of choice.
This engine should be good to go.


Edited by zeng (02/21/18 10:28 AM)

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#4673083 - 02/21/18 11:09 AM Re: 73 Corvette with unknown oil mileage report [Re: Hawkfanatic]
Hawkfanatic Offline


Registered: 11/30/10
Posts: 10
Loc: Northern KY
Thanks everyone. To answer some questions and provide more info.. Car and engine have 35,000 miles. It is a 4spd manual. Car is in very good condition, but it sat for most of 20 years before being pulled from a garage. I am thinking some of this wear might be from dry metal parts.

Heres some pics of our inspection at my house on Sunday.
_________________________
2006 Toyota Tundra Double Cab TRD 4x4
1999 Pontiac Trans Am Firehawk
1991 Pontiac Firebird Formula

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#4673106 - 02/21/18 11:26 AM Re: 73 Corvette with unknown oil mileage report [Re: Hawkfanatic]
69GTX Offline


Registered: 09/23/15
Posts: 3742
Loc: Connecticut
That car is pretty darn mint. Someone obviously cared well for it before it was put up. Not likely they'd park it with an OCI of 15K-25K miles. The recommended oil for that car was never a 20 grade. Why would anyone use that? And a 4 speed no less which is even more reason to use a 30 grade or higher. And OCI's for that car were originally around the 3K mark. Why would any caring owner push a 25K OCI on such a car, even with modern synthetics? It's a 4 barrel carb'd car which fouls up the oil a LOT sooner than today's FI/DI cars. More than likely it's a 30 grade oil in there and probably with average miles for OCI's of the 1990's to early 2000's. Only 2 engine choices for 1973 Vette....350 or 454.

There could be 10,000 miles on that oil. But probably more likely it's only 2K-6K miles.
_________________________
----------------

2002 Lincoln Cont 4.6L DOHC/ 81K mi /PPlat 5w30/FUG XG2
1999 Camaro SS M6 /19K /Mobil 1 0w40 /Fram UG /GM MTL-ATF
1969 Ply GTX/RRs

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#4673107 - 02/21/18 11:27 AM Re: 73 Corvette with unknown oil mileage report [Re: Hawkfanatic]
dernp Offline


Registered: 10/18/12
Posts: 519
Loc: SW Fla
Very nice
_________________________
2014 Honda Civic 1.8 28k TGMO 0w20
2016 Honda Civic 1.5T Mobil 1 0w20
2011 Tundra 5.7L 83k TGMO



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#4673152 - 02/21/18 11:56 AM Re: 73 Corvette with unknown oil mileage report [Re: Hawkfanatic]
Hawkfanatic Offline


Registered: 11/30/10
Posts: 10
Loc: Northern KY
From what I understand, the car was bought by a young guy in the late 70s/early 80s who had it for a few years, but then died unexpectedly. The car then went to his father who kept it as a sort of memorial to his son and never drove it. When he died roughly 20 years later, it was sold as part of the estate.
_________________________
2006 Toyota Tundra Double Cab TRD 4x4
1999 Pontiac Trans Am Firehawk
1991 Pontiac Firebird Formula

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#4673182 - 02/21/18 12:15 PM Re: 73 Corvette with unknown oil mileage report [Re: Hawkfanatic]
motor_oil_madman Offline


Registered: 11/29/09
Posts: 4719
Loc: Houston, Texas
Does it sound Okay?
_________________________
2007.5 dodge cummins 6.7 liter. Chevron Delo400 15w40. 7000 mile or 250-300hr intervals.


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#4673361 - 02/21/18 02:37 PM Re: 73 Corvette with unknown oil mileage report [Re: Hawkfanatic]
Hawkfanatic Offline


Registered: 11/30/10
Posts: 10
Loc: Northern KY
Yes, car is smooth and quiet. No smoke, no ticks. A strong car for what it is.
_________________________
2006 Toyota Tundra Double Cab TRD 4x4
1999 Pontiac Trans Am Firehawk
1991 Pontiac Firebird Formula

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#4673503 - 02/21/18 04:22 PM Re: 73 Corvette with unknown oil mileage report [Re: Hawkfanatic]
Char Baby Online   content


Registered: 05/25/05
Posts: 9751
Loc: ROCHESTER, NY
Wow, very nice. I have nothing else to contribute!
_________________________
"Retired"
'80 Firebird FORMULA V8/4bbl-purchased "NEW"
'06 Mazda 3i 2.0L
'15 Nissan Altima 2.5 SV

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#4673527 - 02/21/18 04:47 PM Re: 73 Corvette with unknown oil mileage report [Re: Hawkfanatic]
DuckRyder Offline


Registered: 10/20/05
Posts: 4111
Loc: Atlanta
Blackstone once wrote on one of my reports that old oil can turn ďacidicĒ and cause these sort of readings. (search post started by me, its probably here, think it was the F100.)

SBC is not expensive to overhaul even if it needs it, Iíd buy the thing if he wants it, it looks like a nice car... Iíll probably offend the purist but it needs a 383 with a roller cam anyway... cool
_________________________
Robert
  • 2007 Toyota Prius Touring
  • 2005 Honda Civic Sedan
  • 1972 Ford F100
  • 2012 Volkswagen Jetta TDi

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#4673620 - 02/21/18 06:05 PM Re: 73 Corvette with unknown oil mileage report [Re: 69GTX]
zeng Offline


Registered: 09/01/15
Posts: 2095
Loc: Malaysia
Originally Posted By: 69GTX
More than likely it's a 30 grade oil in there and probably with average miles for OCI's of the 1990's to early 2000's. Only 2 engine choices for 1973 Vette....350 or 454.

There could be 10,000 miles on that oil. But probably more likely it's only 2K-6K miles.

I stand corrected.
You're probably right with a xW30 on 6-10k miles (with shear thinning being reversed,and onto thickening) AND many long years ..

Edit:None of fuel dilution btw.


Edited by zeng (02/21/18 06:11 PM)

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