Oil advice for low mileage vintage Cadillac

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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?
 
You can continue with what you are doing or you can do the same thing with any good conventional 10W-30.

Now, we need to see a picture of that jewel.
 
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???
 
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!
 
Alrighty, here's a pic. Bought the car from Barrett-Jackson a couple years ago with only 2800 miles on it.

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Awesome car! Is the paint original? Seems the door color is a bit off from the fender.
 
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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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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.
frown.gif

I miss the the sound of WOT from that big 425!
 
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?
 
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.
 
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.
 
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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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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