Author Topic: Does 1977 Eldorado require oil additive?  (Read 360 times)

Offline Rockne Smith

  • Posts: 20
  • CLC Number: 31405
  • Name: Rockne Smith
Does 1977 Eldorado require oil additive?
« on: February 29, 2020, 11:50:07 AM »
Local mechanic recommended I add zinc additive (I believe he said)  to Mobil One oil used in 1977 Eldorado 425.  He said valves need it.  Any thoughts?  Engine has 45,000 miles and runs like a top.  I don't know what oil was used prior to my change to Mobil One. 

Offline Eric DeVirgilis CLC# 8621

  • Posts: 7038
  • Name: Eric DeVirgilis
Re: Does 1977 Eldorado require oil additive?
« Reply #1 on: February 29, 2020, 11:54:42 AM »
Generally recommended with older engines not having roller lifters.
A Cadillac Motorcar is a Possession for which there is no Acceptable Substitute

Offline 35-709

  • Posts: 5360
  • The most valuable antique is an old friend.
  • CLC Number: 4719
  • Name: G. Newcombe
Re: Does 1977 Eldorado require oil additive?
« Reply #2 on: February 29, 2020, 07:56:34 PM »
Don't know how much you really need extra zinc in a well broken in engine but it is worthy to note that, depending on which Mobil 1 you use, you may or not need extra zinc anyway.  Not all Mobil 1 oils are formulated the same as far as ZDDP is concerned.  For this reason I use Mobil 1, 15W-50 exclusively in all of my flat tappet engined cars --- year 'round (see my list below), Phosphorus is 1200 PPM and Zinc is 1300 PPM, plenty enough and at 15W-50 you can use it in the northern climes (maybe not Alaska  :)).

Engines used in my cars below --- 2 - 472s, 1 '70s vintage Chevy 350, 1 '68 Pontiac 400, & 1 '73 Ford 460.
Not listed is the engine in the '42 Cadillac  that I sold shortly after I got it --- a pig in a poke --- a whole 'nother story.
« Last Edit: February 29, 2020, 08:06:27 PM by 35-709 »
1935 Cadillac Sedan resto-mod "Big Red"
1973 Cadillac Caribou - Sold - but still in the family
1950 Jaguar Mark V Saloon resto-mod - Sold
1942 Cadillac 6269 - Sold
1968 Pontiac Bonneville Convertible
1935 Glenn Pray - Auburn Boattail Speedster, Gen. 2

 

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