Oil advice for low mileage vintage Cadillac

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246
Location
Eastern U.S.
I have a 1979 Cadillac Coupe DeVille with 9,000 miles on it (not a typo!). It has a 425c.i V8 carb/gas engine (flat tappett). I'm still running a catalytic converter on the car ('Vette style cat). Right now I'm using Shell Rotella T 5w40 syn (CI-4). Since this isn't a daily driver, I'm only putting about 2,000 miles a year on the car. Should I stay with a syn, and change once a year, or go dino and change twice a year? Also, I don't want too much zddp to hurt the cat, but want enough to prevent tappett/cam wear. Winter temps in my area (NC) rarely go below 25 degrees (car is also garaged and usually not taken out in extreme cold weather). Not sure I want to keep using diesel oil, so what are some choices for my situation?
 
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15,056
Location
Canada
Nice car! Don't hear of 425-powered Caddy's still around much. If you're comfortable with what you're doing, I'd stick with it. If you WANT to go to a twice a year change, I'd use Rotella 10W-30. Pics???
 
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1,034
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GA, USA
They offered a 425 in '79?! Wow! I remember driving my dad's '71 Fleetwood (?) with a 472. Even though the car was as big as a dreadnought I remember driving up a steep grade with 5 adults + luggage on board and the car didn't even skip a beat - MONSTER torque!
 

Rumble

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246
Location
Eastern U.S.
Alrighty, here's a pic. Bought the car from Barrett-Jackson a couple years ago with only 2800 miles on it. [img][/img]
 

Rumble

Thread starter
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246
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Eastern U.S.
Yes, the paint is original. That may be a sunlight thing with the pic, plus, I'm clueless about camera settings. Blokey, the '79s were the last year for the 425 engine. In fact, only used from '77-'79. That's a 3 year body style as well.
 
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349
Location
Illinois
My grandma bought a '79' Coupe from her neighbor who had to stop driving, it was in near new condition with only 28k miles on it. She bought it for my dad which meant when I got my license, I learned how to drive in that car myself. I loved the way that car drove and like how I looked like a pimp driving it through my local downtown suburbia. hehe. Ours was a maroon color. This was way back in 1995 and I still think about that car, mostly how I never put to use those roomy backseats during my highschool years. \:\( I miss the the sound of WOT from that big 425!
 
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15,056
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Canada
Thank-you. Beautiful car. Heck, on something THAT nice, I'd change out RTS 5W-40 twice a year! Do you take it to shows?
 

Rumble

Thread starter
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246
Location
Eastern U.S.
 Originally Posted By: addyguy
Thank-you. Beautiful car. Heck, on something THAT nice, I'd change out RTS 5W-40 twice a year! Do you take it to shows?
Thanks. I've only taken it to one show so far. It won a trophy, one of top 50 cars. Kinda hard competing with all the muscle cars, lol! Thanks for the comments everyone, and the oil advice.
 
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8,859
Location
Texas
 Originally Posted By: Rumble
I have a 1979 Cadillac Coupe DeVille with 9,000 miles on it (not a typo!). It has a 425c.i V8 carb/gas engine (flat tappett). I'm still running a catalytic converter on the car ('Vette style cat). Right now I'm using Shell Rotella T 5w40 syn (CI-4). Since this isn't a daily driver, I'm only putting about 2,000 miles a year on the car. Should I stay with a syn, and change once a year, or go dino and change twice a year? Also, I don't want too much zddp to hurt the cat, but want enough to prevent tappett/cam wear.
Ahh, the last year of the first generation of "downsize" Cadillacs (hard to believe the 77-79s are a "downsize" until you park one next to a '76, but it is!). Beautiful car (I saw the picture further down the thread). Don't worry about the ZDDP hurting the cat- the oils that were in use when that car was new had a LOT more than current Rotella T. I'd do exactly what you're doing if it were mine.
 
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19,479
Location
Chicago Area
If you switched to dino, I don't see why you'd change it twice a year, with those low yearly miles. But since the Shell Synthetic is so reasonable, why not just stick with it anyway. As for your cam/lifters, they are broken in and are not a real concern for wear with modern oils. That engine got power from it's SIZE, not hot cam profiles and high spring pressures.
 
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782
Location
Alberta
 Quote:
Not sure I want to keep using diesel oil, so what are some choices for my situation?
Almost all HDEO's like Rotella T have a dual diesel/gas engine rating, so they are fine for gas engines. With a high quality synthetic like 5W-40 Rotella, you could run a lot farther than 1 year 2k miles -- I'd say 2 years 4k miles would be no problem. The conventional Group II based 15W-40, 10W-30 Rotella HDEO's are high quality high performance oils these days, and you could run them 1 year 2k miles easily with synthetic like performance. There really won't be any difference between these Group II based conventional oils and synthetics at such a low mileage usage. The conventional HDEO's would be a less expensive 1 year option to changing out the synthetic 5W-40 at such low miles.
 
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