Synthetic Oil in the Northstar


RASCARS
08-28-2006, 07:55 PM
I'm new to this portion of the forum. I just purchased my first new(to me) Cadillac; a 2005 Deville DTS with 7,000miles.
My question concerns the use of Mobil ONE, or any synthetic oils. I read the owners manual and it is silent to this issue. The original owner of my car (and a good friend) told me that on the one oil change he had done at the dealership at 3,500 miles was done with regular mineral oil, not synthetic. He did not question the service writer.

Is there any reason NOT to use synthetic oil in the Northstar. I have been a fan of Mobil ONE almost since its introduction. I also use the Mobil ONE filters (expensive, but I figure for a few $$ more I may get a bit more protection).

I know that Northstar engines had issues with seals in the late 90's, but I understand that GM corrected this in 2000.

I would appreciate any information and recommendations on the use of synthetic oil in Northstar engines and and resources that anyone can direct me to so I can use the proper oil in my new baby.

Thank you and have a great week,
RASCARS
:newbie:

maxwedge
08-28-2006, 08:24 PM
I'm new to this portion of the forum. I just purchased my first new(to me) Cadillac; a 2005 Deville DTS with 7,000miles.
My question concerns the use of Mobil ONE, or any synthetic oils. I read the owners manual and it is silent to this issue. The original owner of my car (and a good friend) told me that on the one oil change he had done at the dealership at 3,500 miles was done with regular mineral oil, not synthetic. He did not question the service writer.

Is there any reason NOT to use synthetic oil in the Northstar. I have been a fan of Mobil ONE almost since its introduction. I also use the Mobil ONE filters (expensive, but I figure for a few $$ more I may get a bit more protection).

I know that Northstar engines had issues with seals in the late 90's, but I understand that GM corrected this in 2000.

I would appreciate any information and recommendations on the use of synthetic oil in Northstar engines and and resources that anyone can direct me to so I can use the proper oil in my new baby.

Thank you and have a great week,
RASCARS
:newbie:
There is no info out there that warns against the use of top quality synthetic oil of the proper weight and service classification.

caddydaddy
08-29-2006, 07:11 PM
If you are to use a synthetic, Mobil 1 is the only one that GM approves. I use Mobil 1 in my 2000 STS and have since it was new. I now have 40k miles on it with no problems.
I also go by the oil life monitor for oil changes, and usually get over 8,500 miles between oil changes. 3,500 miles is much too soon, and is a waste of money. As per your owners manual, don't go over 12,500 miles or 1 year between an oil change. But most likely the oil life monitor will tell you to change it before then.

RASCARS
08-29-2006, 10:04 PM
Thank you Caddy Daddy
I need to hear from owners like you that have used Synthetic oil in their Northstars. I also prefer Mobil ONE. I will use the monitor as a guide, but I still believe in 6 month oil changes regardless of mileage. For me, it is sleep insurance for the engine of all my cars.

Do you change it yourself or do you use the dealer.
I have always done most of this simple maintenance myself. Is there any issue on Caddy's that only the dealer can do routine maintenance?

Have a great week.
RASCARS:)

caddydaddy
08-29-2006, 10:38 PM
Thank you Caddy Daddy
I need to hear from owners like you that have used Synthetic oil in their Northstars. I also prefer Mobil ONE. I will use the monitor as a guide, but I still believe in 6 month oil changes regardless of mileage. For me, it is sleep insurance for the engine of all my cars.

Do you change it yourself or do you use the dealer.
I have always done most of this simple maintenance myself. Is there any issue on Caddy's that only the dealer can do routine maintenance?

Have a great week.
RASCARS:)

Well, the 6 months is up to you, but just know that GM put a lot of time and effort into establishing the figures for the oil life monitor. I change mine when it's near 10%, and that's very conservative! I even had the oil analyzed, and it was in great shape with 8,500 miles on it! The lab recommended I try 9,500 miles next time. But if it helps you sleep better at night, change it! :)
I do most of the work on my Cadillacs myself. You don't need to go to the dealer to have the warranty be valid. I believe it's the Magnuson Moss Act that states that you can do your own maintenance and not have to go to the dealer to keep the warranty valid.
I would just keep the reciepts for the oil, filter, or whatever you have replaced or repaired as proof that it was done. I also keep record of it in the maintenance section of the owners manual.

RASCARS
08-30-2006, 08:35 AM
Thanks Caddy Daddy,
Keepimg receipts to verify the maintenance log is excellent advice.

I noticed your 79 SDV on your signiture. :cool: I just sold my 79 coupe. I love that series Caddy. I'm going to replace my 79 with another 79 coupe next year.
Great cars, great styling, very reliable.

Thanks for your input on the Mobil ONE.
Have a great Labor Day

RASCARS

caddydaddy
08-30-2006, 10:41 AM
Yeah, my '79 has been a great car. It was my first car, and I've had it for almost 10 years. It's still a work in progress and I'm turning it into a muscle car. I just installed a posi rear end a couple of months ago.

maxwedge
08-30-2006, 03:43 PM
Yeah, my '79 has been a great car. It was my first car, and I've had it for almost 10 years. It's still a work in progress and I'm turning it into a muscle car. I just installed a posi rear end a couple of months ago.
Caddydaddy, changed the engine in the 79, should be a 425? I think I asked you this sometime back, sorry if I forgot.

caddydaddy
08-30-2006, 08:11 PM
Caddydaddy, changed the engine in the 79, should be a 425? I think I asked you this sometime back, sorry if I forgot.

Yes, the original engine was a 425. I replaced it about 7 years ago with a 1972 472.

maxwedge
08-30-2006, 08:15 PM
Yes, the original engine was a 425. I replaced it about 7 years ago with a 1972 472.
Cool, thought I remembered that.

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