Switch to synthetic in 1975 buick 350 engine

reedsteed2k · Aug 16, 2006

Bought this vehicle (1975 Century) a short time back (great 1st car for the new driver in my house. It's built like a tank!). Changed with dino when purchased.

85k miles on vehicle. Engine is clean. No visible leaks. Starts and runs great.

Was thinking about a switch to synthetic, but have read about leaks resulting. I'd like to get some thoughts on the subject. Anyone have any experience with doing similar in a vehicle of this vintage.

Thanks.

CBDFrontier06 · Aug 16, 2006

I attemtped to convert my 1978 Chevy Monza 2.5 I4 over to syn and shortly after, the rear main, valve cover and lifter cover gaskets started leaking. I switched to Castrol and replaced those seals, but stayed with dino before anything else sprung a leak.

JAG · Aug 16, 2006

I say don't test your luck. It's not worth the risk. 31 year old seals will have hardened and shrunk and one good thing about dino oil is it can plug the gaps with crud (false seals). Take them away and the floodgate can open.

reedsteed2k · Aug 16, 2006

So, do you think maxlife dino would be in order, or could that cause me some troubles too?

JAG · Aug 16, 2006

Sounds good. Take your pick: Castrol HM, Pennzoil HM, or Maxlife.

Rob Taggs · Aug 16, 2006

I have a 1976 Buick Lesabre. Yes, it is built like tank. I put Mobil 15w-50 in it once and didn't get any leaking. I would not push my luck either using it after all I have read here on this site. One that struck me was how well the Mobil cleaned up the engine. It was not bad to begin with but, ever time I pulled the dipstick it had old bits of gunk on it.

Volvohead · Aug 16, 2006

A-R-X.

Do that first. If it starts leaking after that, then deposits were maintaining a faux seal and you would have had worse leaks going to a synthetic. Remedy the tired seals at that point. Using dirt as a sealant is not very reliable in my book.

But if it stays tight, you've now got a clean engine ready for the changeover, and that includes the seals. And that also includes the ringpacks.

After 31 years, I'd ARX it regardless of mileage. ARX won't harm it.

UncleS2 · Aug 16, 2006

With those 31 year old seals, I'd stick with dino, probably one of the high-mileage dinos mentioned above. JMO

LargeCarMan · Aug 16, 2006

Ok...I will play the other side of the coin. Been there and done it too. 68 Fury, 74 Newport, 78 Dodge. One leaked the others did not.

First I would find the rebate form for SYNTHETIC Maxlife from Valvoline and take the plunge. After your first OCI of this at 7.5 K go for the 10-40 Amsoil.

What have you got to loose? YOU KNOW you want to go SYNTHETICS....So just do it!

MIAMI-DADE · Aug 16, 2006

quote:

Originally posted by Stuart Hughes:
With those 31 year old seals, I'd stick with dino, probably one of the high-mileage dinos mentioned above. JMO

I wouldn't even think about putting in synthetic in that car.

BTW I think thats what Kojack used to use to get around NYC in the 70's.The 75 Buick Century was good car and the 350 was one of the best engines ever made.

bighead · Aug 16, 2006

Was wondering if anybody was going to mention the fact the engine is so old, would SM oils be too "additive deficient" to protect it? This is a serious inquiry on my part, as I keep reading HDEO recommendations for older cars like this...

nemir · Aug 16, 2006

I use max life 5/30 full synthetic in my '78 Lebaron /6 and in my '80 Lebaron 318. NO PROBLINTOS.

427Z06 · Aug 16, 2006

quote:

Originally posted by Volvohead:
A-R-X.

Do that first. If it starts leaking after that, then deposits were maintaining a faux seal and you would have had worse leaks going to a synthetic. Remedy the tired seals at that point. Using dirt as a sealant is not very reliable in my book.

But if it stays tight, you've now got a clean engine ready for the changeover, and that includes the seals. And that also includes the ringpacks.

After 31 years, I'd ARX it regardless of mileage. ARX won't harm it.

I like this advice best.

Clyde65 · Aug 16, 2006

10W-40.

Mike_dup1 · Aug 18, 2006

It would be highly unusual for any pre-1990 domestic vehicle to not leak oil. Common knowledge the mfg. paid little attention to fixing oil leak problems in thier engines. Even today, go take a walk around a Wal-Mart parking lot when it empty if that possible. You will be hard pressed to find a spot where there no leaked oil. Of course, some fools change thier oil right in the parking lots. Seen the mess and used filter laying there once. I know a guy who is on cart partol at local SC and he says he had found it all in the parking but the worse are throw away diapers. Last year a guy bleeding to death, robbed and stabbed in the lot. He lived but was lucky, it was very cold out and that may have saved him.

Steelhead · Aug 18, 2006

use a 5w40 diesel rated synthetic HDEO... old flat tappet cam engines do not live long on straight SM rated oil...not enough AW and FM's for all that iron turning and burning
or throw in a full bottle of VSOT or SLOB, increases AW's and FM's
no modern sensitive cat. converter to worry about in this V8 iron freeway warrior
Shell Rotella T is a quality 1 to use, others out there on your oil dealer's shelves...Mobil 1 Truck&SUV or Amsoil makes a diesel syn
http://www.rotella.com/products/rotella_t_synthetic.html

Rickey · Aug 18, 2006

I second the Rotella T HDEO conventional or synthetic. I would personaly give preference to the conventional for this application due to the concerns with seals and "synthetic" This engine with its flat tappets may possibly need more anti wear agents than an SM rated oil can provide. Maybe I'm wrong about this. Is there definitive proof one way or another? An extra dose of zinc (within reason) will help this engine live longer IMHO. For SM rated oils a bottle of Specialty Formulations SX-UP,http://specialtyformulations.netfirms.com/store/nfoscomm/catalog/index.php , CD-2 Street Legal Oil Boost (SLOB), GM engine oil suppliment, VSOT (Valvoline Synthetic Oil treatment) or similar should help protect this vintage engine.(Dern that vintage statement is making me feel old) And I might add that is one fine ride by any standard. Rickey.

TheTanSedan · Aug 18, 2006

I have been changing old, used cars to synthetic since 1982. I can hardly see "leaking seals" as a reason NOT to change over. After all, they're already failed. Which means dirt getting in, not just oil leaking out.

If it leaks, fix it.

I've posted a number of times on this subject, and my success in doing so. In all cases, oil consumption either declined or stabilized or both.

Nowadays, with ARX, FUEL POWER and LUBE CONTROL, the opportunity to have the car running better than ever is not possiblity. It is fact.

Just remember that flat tappet cams don't live well on most of today's oil. Either choose a dino like CHEVRON Delo 15W-40 [diesel/gas] or some other with Molakules oil supplement (SX-UP @ Specialty Formulations ; see sponsor list), or a synthetic which still has the proper amount of "old" additive package.

Don't forget the trans and rear end either. I like ARX and synthetic in them just as much.

reedsteed2k · Aug 18, 2006

quote:

Originally posted by MIAMI-DADE:

quote:

Originally posted by Stuart Hughes:
With those 31 year old seals, I'd stick with dino, probably one of the high-mileage dinos mentioned above. JMO

Click to expand...

I wouldn't even think about putting in synthetic in that car.

BTW I think thats what Kojack used to use to get around NYC in the 70's.The 75 Buick Century was good car and the 350 was one of the best engines ever made.

I'll have to tell my kid about Kojak. He'll get a real kick out of it.

Like I said it's safe because it's built like a tank. Runs well and looks good. I picked it up for nearly nothing, and I save money on insurance by making the kid primary on it. AND the kid loves the car because it has character. Only problem is the gas milesage, but it's ok by me. It may keep him from going too far from home due to gas prices.

I think I'm going to go the regular maxlife route just to be safe.

Thanks to everyone.

dave1251 · Aug 18, 2006

Steelhead
Member
Member # 8092

posted 18 August, 2006 06:29
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use a 5w40 diesel rated synthetic HDEO... old flat tappet cam engines do not live long on straight SM rated oil...not enough AW and FM's for all that iron turning and burning

Where is the proof to all of these calm's?

That's all I ask and I dont mean the biased Hot Rod article either. Has there been a massive engine's failure in the last 10 years?

Switch to synthetic in 1975 buick 350 engine

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