: 98 deville best oil for low oil oil consumption?

02-06-10, 11:27 PM
i know all about how the northstars burns oil and its not bad for the motor but i was wondering if their is a specific brand out their that doesnt burn the most. i am currently using mobil 1 full synthetic and it seems like i burned a quart off in about 800 miles and before i was using castrol syntec with the same results. anyone have any suggestions?

02-07-10, 12:58 PM
It's the motor, not the oil. Have you read the Technical Archives at the top left on oil consumption?

02-07-10, 01:25 PM
try using conventional oil, synthetic usually burns more and leaks more.....if the engine allows this.

Try pennzoil or quaker state. Ive heard some guys say one or the other makes it worse or better.

Ablsolutley no need for synthetic in this engine, alot of these engiens dont even have oil coolers and thats where synthetic oil shines, it can shed heat faster than conventional.

02-07-10, 03:13 PM
ok but now that i have the synthetic in there i heard i cant switch back to conventional or im going to ruin the motor?

02-07-10, 03:33 PM
I also have a 98 deville, using synthetic, Penzoil, and seeing about the same miles per quart...and yes, I know it is the engine, I might consider going back to a conventional oil...which is what it had before I bought it..I've got about 51K miles on it

02-07-10, 05:03 PM
First, Synthetic motor oils do not burn more and leak more. Old wives' tale.
I run 5W-30 Pennzoil Platinum synthetic and WIX 51522 filters, use a quart in 4,000 miles + (mostly rural and highway), and not one leak.

You can switch motor oils to your hearts' content and it will hurt nothing - only your wallet.

Run the recommended weight oil, dino or synthetic, that you're happiest with and don't overfill the pan. The correct level for a Northstar is halfway up the dipstick hashmark, cold. If you continually fill it to the top mark it will quickly burn off the overfill.

Take Ranger's advice and read the entire Cadillac Technical Archive, up in the black bar ^^^, particularly the one titled "Occasional full throttle operation is good for your engine" (or close.......)

IF your car has the HD towing package the oil cooler is in the hot side of the radiator tank, so the oil will always run at or above hot side coolant temperature: it must run this hot in order to vaporize acids and moisture from condensation. The resulting vapor is returned to the intake manifold by the PCV system for burning in the combustion process. (BTW, if you overfill a Northstar the oil is whipped into foam and vapor and the PCV system does its job and happily burns off the excess........)

02-07-10, 06:09 PM
FYI - synthetic oils also do not transfer heat as well as conventional oils, that's what allows it to not break down as fast and last longer.

02-07-10, 07:11 PM
Not quite - you might want to Google "synthetic oil heat transfer".

They transfer heat just as readily, but are more stable at higher temperatures than conventionals.

02-07-10, 08:50 PM
If that's the case then why in all of our testing could we only get half as many laps out of the valve springs and rear gears as conventional? These components failed from excessive heat when mobil 1 was used. Not sure what you found on google but these were real world tests done in real cars.

02-08-10, 10:00 AM
"Half as many laps"............are we talking apples and oranges, as in professional track racing against a daily driver car engine ?

Does your race engine (unspecified type) have the same cylinder head oil flow as a street engine (unspecified type) and does it operate in the same RPM ranges as a typical Northstar (majority engine in these FWD Forums) ?

What was Mobil 1's reply when you informed them that you were experiencing valve spring failure from excess heat due to Mobil 1 being inadequate for a race engine ?? If you can prove your theory, you can certainly bring down one of the biggest names in racing sponsorship. That would be quite a feat.

Not saying you're wrong in your spring failure theory, but I'll bet Mobil Oil would beg to differ.

(EDIT: If your theory was correct, why do several world famous car builders specify Mobil 1 for their high performance engines ?)

02-08-10, 09:33 PM
well you can have your opinions, but synthetic will leak more at storage temp, like overnight in the garage, take a look at my half case thread.....thats all synthetic oil that coated my cars entire undercarriage.

same on my jeep, if theres a leak, synthetic finds it faster.......

i bought the syn because menards was selling cases for $5 after rebate, i will not be buying any more synthetic oil.

02-09-10, 12:44 PM
I have heard that, but don't know if it is true or not. Never used synthetic.

02-10-10, 02:29 PM
ok guys lets stop fighting all i wanna know is if i switch back to conventional from synthetic am i going to damage anything?

02-10-10, 04:03 PM
No harm in switching from Dino oil to synthetic or back. Best to change the filter when you do switch.

Synthetics will "creep" more than Dino oil, which is why you see some cars that never leaked on Dino oil develop some drips when you go to synthetic.

02-10-10, 04:12 PM
yeah i should of just put regular dino in there it seems the more i wanna take care of it the more i end up getting frustrated thanks alot buddy

02-10-10, 04:51 PM
ok guys lets stop fighting all i wanna know is if i switch back to conventional from synthetic am i going to damage anything?

02-10-10, 05:18 PM
why would you need synthetic oil in the northstar? the way it uses oil you add a quart or two at least between oil changes.. it is constantly seeing clean oil.. i think synthetic oil is a waste in this motor.. especially if you're old fashioned like me and change your oil every 3,000 miles..

02-10-10, 11:01 PM
i change every 3000 with the synthetic...but i want this motor to last a very long time so i figured i would get the best stuff for it but of course every time i try to do some good i end up doing more harm so screw the synthetic time for the regular stuff. im only 16 so spending 20$ less on oil wont hurt lol. i just heard u cant switch back because it conditions seals and blah blah blah but if you guys say its alright then its alright :thumbsup: thank you alot!

02-11-10, 11:58 AM
undertaker, i know you want your engine to live but my opinion you are wasting tons of money on oil. i read a good topic some time ago, in this forum i believe, about how good the oil life monitor system is on these cadillacs. don't ask me to find it, sorry. gist of it was that gm put a ton of miles (22MM is the number that comes to mind), money and time developing it, and it works. you don't need to change oil ever 3,000 miles - change it when the monitor tells you to change it. don't forget you are throwing a quart of fresh oil in every 1,000 miles or so.

i use this car mostly for highway travel. i end up changing the oil about every 10,000 miles. when the oil life monitor gets down to 10% or so, time to do it. anything higher, and i think you are wasting oil and filters. i've got around 130k on my car, and clean burning and plenty of life left (knock on wood). and still fun to drive and very comfy on the highway which is why i keep this car.

of course you do whatever you like, but synthetic every 3,000 miles seems way over the top and i'll bet it makes zero difference in engine longevity. something else will give first. dino oil when the dashboard tells you and i'd bet you get the same result. i'm sure others here feel differently but i've never run synthetic in any road vehicle i've owned and i've run up mileage in many vehicles over the years.

02-11-10, 01:36 PM
yeah im just paronoid my dad never really payed any attention to his oil life monitor in his saturn just changes every 2000 but i guess your right im wasting money for no reason lol thanks for the money saving information = )

02-11-10, 05:00 PM
2 and 3K oil changes are old school and are pushed by people who make money changing your oil like Jiffylube. Like Gofish, I do mostly highway driving and can get the full 12,500 miles out of an oil change according to the OLM, but I also do mine at 10,000 just for the ease of remembering when to do it, 50K, 60K, 70K etc.

02-11-10, 06:37 PM
Also don't forget- Northstars get oil adds between changes, sometimes, and they do hold a fair bit of oil. More crankcase capacity, the longer the stuff should last...

02-11-10, 07:34 PM
Here in Phoenix, we have some pretty severe summer heat; here is what I do:

In my '97 ETC, I use Walmart dino 10W-30 $8.19 per 5 quart jug - seems to work just fine - I change the oil per the OLM.

I run Mobil One (from Costco - about $4/qt. with coupon) in my 2000 DTS, my 2004 Grand Prix GTP (supercharged) and my 2005 Lincoln LS (V-6). My reasoning is that the DTS doesn't have the oil cooler, so the oil may run hotter; the Grand Prix is supercharged, so the oil may run hotter; the LS engine works pretty hard; all of these things COULD cause the engine oil to deteriorate during the wickedly hot (110+ degrees is normal) summer months. I change the DTS and GP oil once a year or when the OLM tells me to. The LS does not have a monitor - normal service oil change interval in the manual is 5K miles (severe is 3K), which I stick to pretty closely, or maybe a little over - I figure the syn gives me a little more protection. The LS manual actually calls for a 5W-20 dino-syn blend - this one to be exact:


Over the years, I have used cheap oils, like the Walmart I put in the ETC, and I have used expensive oils like Mobil One - as long as they have the proper ratings, they all seem to work OK. I am not aware of any lubrication related failures I have experienced. Why do I use syn at all? Well, on the newer cars, it does give me some added peace of mind when beating on the engine, and after all, it only costs about twice was much, or $2/quart more than dino, so I figure what the hell

02-11-10, 10:09 PM
:devil: yeah..............them thar' sinthettics leaks out of them engines like water. You gotta put in some thickener to keep it all in - molasses works good. So does 80-90 gear oil or $12.50/pint magic oil stiffener.