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:cool2: I just bought a 95 deville with 71,340 miles on it and I would like to know if the 4,9 motor would be happy with the synthetic oils . Also would it help the motor run cooler and aid on getting better mileage?:)
 

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1987 D'Elegance 4.1L 1993 Eldo 4.9L 1993 STS 4.6L N* Z rated
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The best type of oil you can use in your 4.9 is Rotella T 15W-40. 15W-40 is the best oil for the 4.1, 4.5 and 4.9L engines.
 

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2003 STS w/BoseNav, 1993 Deville, 1985 Deville
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I used Mobil 1 in my 1993 Deville (4.9L). The engine is still purring happily at 298,000 miles and doesn't burn *any* oil.

I also used Mobil 1 in my 1985 Deville (4.1L). Engine ran until 238,000 miles when the water pump suffered a catastophic failure.
 

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1988 SDV; 1997 SDV D'Elegance
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A few years ago I switched from DINO juice to synthetic MOBIL 1 in my 1988 Sedan Deville (just clocked 300,000 on the Odo). I use MOBIL 1 synthetic in the engine, transmission and K&N filters for the oil and air. Also, LUCAS UCL goes into the gas tank now for each fill up and the LUCAS synthetic auto trans stabilizer was put in this year to help smooth out the shifiting. After that many miles, a little kindness to the tranny won't hurt anything.

I used to use SLICK 50 in the engine/tranny and power steering, but now prefer the LUCAS brand for supplemental slipperiness.

My '88 has been feted by more than a few mechanics for it's continued gliding action at all speeds - and I intend to keep it that way for as long as possible.
 

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1992 Town Car Cartier & 2014 Accord LX MTX
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I believe the 4.9s love that Rotella 15W40 Diesel oil.

Or is that just the early 4.9's?
 

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2003 STS w/BoseNav, 1993 Deville, 1985 Deville
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I used to use Rotella in my Ford Super Duty 7.3L Powerstroke Diesel truck. That huge engine took almost four gallons of it!!!! The oil filter took about a quart all by itself. I bought it by the gallon.
 

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1987 D'Elegance 4.1L 1993 Eldo 4.9L 1993 STS 4.6L N* Z rated
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The Rotella has been recommended by some of the most knowledgable cadillac fans :yup: . Best thing besides synthetic oil.
 

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94 Fleetwood Brougham
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Be glad your car isn't under warranty, because Slick 50 voids it. It is very caustic and very very bad for engines and often plugs up oil filters forcing them into bypass, accelerating wear.

Do searches on this site for synthetic oil and you will find a WEALTH beyond imagine on slick 50, synthetics, etc. You will likely reconsider once you read it all.

And supporting dino oil, 300K on dino oil, not bad eh, what can synthetic do that dino oil can't? I have some data on my car (94 Fleetwood LT1) that shows no fuel economy savings from 15W40 Rotella T to 5W40 Rotella T synthetic. My 96 Burb runs 15W40 in WI cold (we are seeing single digits already this year) and no issues at all. Starts up just fine.

Honestly, it is a waste of good hard earned $$.

Frost said:
A few years ago I switched from DINO juice to synthetic MOBIL 1 in my 1988 Sedan Deville (just clocked 300,000 on the Odo). I use MOBIL 1 synthetic in the engine, transmission and K&N filters for the oil and air. Also, LUCAS UCL goes into the gas tank now for each fill up and the LUCAS synthetic auto trans stabilizer was put in this year to help smooth out the shifiting. After that many miles, a little kindness to the tranny won't hurt anything.

I used to use SLICK 50 in the engine/tranny and power steering, but now prefer the LUCAS brand for supplemental slipperiness.

My '88 has been feted by more than a few mechanics for it's continued gliding action at all speeds - and I intend to keep it that way for as long as possible.
 

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94 Fleetwood Brougham
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Recommended by the former guru here for anything with a distributor gear, as it has higher levels of ZDDP antiwear additives than conventional oils.

I~LUV~Caddys8792 said:
I believe the 4.9s love that Rotella 15W40 Diesel oil.

Or is that just the early 4.9's?
 

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85 Eldo Biarritz
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Yup, another "regular vs. synthetic oil" thread has begun! Oy!

It's going to be a lively one again.
:D

Peteski
 

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94 Fleetwood Brougham
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Just carrying on the torch in rememberance! :)
 

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1985 Fleetwood S&S Funeral Coack
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Yes, the additive package in the oil can be useful in the synthetics and the oils mentioned with great favor, but I have an additional factor to keep in mind for the engine in my '85. It has a dent from an impact with a misbehaved tombstone, and the gasket leaks a bit. I have to add often enough that even cheap oil will maintain enough additives! It's a nuisance, but it's only a spoonful a day, so oil will be cheaper than a new oil pan for the forseeable lifespan of the car. I don't seem to burn any oil to speak of. Exhaust reads clean on the emissions control machines and the plugs stay clean. I just have to put new paper down on the garage floor every week and add half a cup of oil.
 

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94 Fleetwood Brougham
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So far my experience in my 5.7L Vortec Suburban with 220K miles and 15W40 Rotella T has been great. No issues with cold starting, even at -10F cold soaked all night. A little slow, but starts right up.

I have 5W40 Rotella T synthetic in my Cadillac LT1 and same temps, cranking speeds seem similar. No issues with either starting.
 

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My car had 79,917 miles on it when I got it in my driveway.

It now has 112,670

It has got Mobil 1 synthetic 10W-30, now the newer "Extended Performance" ever since I got it.... thats all its been getting.

has an oil leak, but it is from the oil cooler lines... not oil related.

dosn't burn any oil, runs great... VERY clean inside...





It is all I would use in my 4.9. If I was to use anything else, yes, it would be 15W-40 Rotella HD Diesel oil..... but I personally much prefer the Mobil 1 :)
 
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