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Topic: Synthetic oil - what weight?

in Forum: C3 Engines

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Synthetic oil - what weight?

Posted: 1/14/10 9:40am Message 1 of 10
tsmith1499
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mount airy, MD - USA
Joined: 8/27/2006
Posts: 71
Vette(s): 1981 Charcoal Met., Silver Interior, Gymkhana Suspension, 27K original miles. It's my daily driver.
I am going to change the oil in my 81' with 28K on the meter. I use synthetic in my deisel pickup and when it's cold it works great. Since I have been driving my car lately I thought it would be nice to put Syn. in it also.  I know this may sound dumb, but do I go with the same as normal oil or a different weight. Never was a fan of synthetic oil until this winter and my F350 7.3 turns over at 20 degrees like it was 80 degrees outside.


1981 Corvette, 26K original miles, charcoal gray, gymkhana suspension, AM/FM/8 track.
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Synthetic oil - what weight?

Posted: 1/14/10 11:16am Message 2 of 10
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Adams' Apple
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Duncanville, TX - USA
Joined: 11/8/2003
Posts: 20214
Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas
I'd say stay with the recommended viscosity for the climate conditions listed in the owner's manual.

A warning, tho...changing to a synthetic based oil on an engine that has had nothing but mineral based oil in it CAN cause leaks to appear. Due to the difference in the molecular makeup of the oil, the particles are smaller than mineral based oils, so they can, and usually will, find any small leak spot that exists, that wouldn't normally leak with the heavier, mineral based oils.



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Synthetic oil - what weight?

Posted: 1/14/10 12:16pm Message 3 of 10
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ebo
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Holland Patent, NY - USA
Joined: 6/3/2008
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Vette(s): #1 *1980 White, Red interior 14,000 mile #2 *1980 Red, Oyster interior 93,000 miles Resto project car, rebuilt to 383 stroker

I'm a big fan of the Synthetic's in my daily drivers, but as for the toys that sit sometimes more than they run I like something I can freshin more often and use a good grade oil non- synthetic.

When buying Synthetic I use the one in the silver jug with a big V on it  as research shows it's on top of the charts and way better than than the container with a big 1 on itWink

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Synthetic oil - what weight?

Posted: 1/14/10 12:48pm Message 4 of 10
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F4Gary
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Grapevine, TX - USA
Joined: 8/26/2006
Posts: 1522
Vette(s): 1972 LT-1 convertible with factory air. 2017 Black Rose Grand Sport convertible.
I use the one with RP on the front.  Wink


   

Synthetic oil - what weight?

Posted: 1/14/10 2:25pm Message 5 of 10
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Gunslinger
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Frederick, MD - USA
Joined: 9/8/2003
Posts: 3398
Vette(s): 1969 convertible L71 427/435 4-speed black interior
I agree 100% with Joel.  While there's absolutely nothing wrong with going to a synthetic, there's also no compelling reason to do so in cars of our vintage.  The real secret is regular oil changes with the appropriate viscosity for the upcoming conditions until the next oil change.

One thing to consider...even the inexpensive house brand motor oils today are better than the finest oils available when our cars were first built.  There's no such thing a a mom and pop oil refinery.  The same bottle of Castrol. Quaker State, etc., you buy today isn's the same as the same bottle a year ago...oils are always being refined and additive packages changed for various reasons...actual improvements, demands made by the auto companies, EPA regulations, whatever.

We do have to worry about ZDDP being removed or greatly reduced in oils that have to be used in flat tappet engines, but that can be dealt with by buying certain brands and grades of motor oil, or using additives such as GM EOS or the old standby, STP.  These and other additives have sufficient ZDDP to take care of any potential problems...and those problems are remote possibilities in most cases.  High compression, high performance flat tappet engine with very stiff valve springs seem to be the most at risk...like some of our Corvettes.


Synthetic oil - what weight?

Posted: 1/14/10 5:16pm Message 6 of 10
Ten15
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East Hanover, NJ - USA
Joined: 9/25/2004
Posts: 525
Vette(s): '68 Black Conv. Matching 327/300 4 Spd. P/S, P/B, P/W, Tele, A/C

Tom,

I've been using http://www.goldenmotorguard.com/cart/ for a while now.

It's availabe in natural and semi-synthetic blends in several grades and it is high (1800 ppm)  in ZDDP.  No additives needed.
 
I use the 10w-40 semi-synthetic (Golden Motor Guard) since my engine has recently been rebuilt.  I used the natural (Motor Guard) 20w-50 prior to the rebuild.
 
Just my 2 cents,
Anthony
 
 



Synthetic oil - what weight?

Posted: 1/14/10 7:51pm Message 7 of 10
greypoupon69
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Irving, TX - USA
Joined: 8/21/2004
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Vette(s): #1 -1969 Corvette Coupe Riverside Gold, black interior,MN,A/C,350/350,PS,PB,window cranks. #2 -2000 C5, black/black, 6 sp, Bose system & lots of buttons.

For me, the Rotella Diesel oil works wonders in the old girl. Wink




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Synthetic oil - what weight?

Posted: 1/14/10 8:12pm Message 8 of 10
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dskopp
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Oak Creek, WI - USA
Joined: 5/21/2008
Posts: 1965
Vette(s): 1981 Great White Shark. Red Interior, 350/190 hp. PS, PB (SS), A/C CC, T-Tops. Served three years in Active Duty Army, then Retired Air Force after 34 years! Badger State Vettes Car Club. 175,000 Original miles!! Now own a 1998 C-5!
Nice to hear from you Micki!!!
Dan



     



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Synthetic oil - what weight?

Posted: 1/14/10 8:29pm Message 9 of 10
sundew
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Eagan, MN - USA
Joined: 6/18/2007
Posts: 427
Vette(s): Gone, but not forgotten: 1974 Coupe Red, matching numbers, Black Interior, L-48 w/ 4 speed; The “Admiral”, also gone and never to be forgotten. 1994 Admiral Blue LT-1 coupe, Black Interior Automatic

Given an '81 does not have a roller cam, I would hesitate to use a synthetic oil. I use 15-40 Shell Rotella-T in my '74. Seems to work just fine.  All of my friends in the local Corvette club use Rotella in the "classic" corvettes. My 2 cents worth.




There is no substitute for low end torque!


Synthetic oil - what weight?

Posted: 1/15/10 2:58pm Message 10 of 10
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lukesvette
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HOWELL, NJ - USA
Joined: 5/18/2004
Posts: 6812
Vette(s): 1979, Targa Blue (72 Color), Pace Car rear spoiler, L88 hood, Dark blue factory interior, 525HP 406, HD 700R4, 370 gears,Steeroids, composite rear spring, TT IIs wrapped in T/A Radials.
I use Syntech - castrol 's hybrid oil - no leaks, great oil pressue - as a synthetic blend, best of both worlds IMHO.....


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in Forum: C3 Engines


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