Change from petroleum oil to synthetic in my Buick?

robert graham

Admiral
Joined
Apr 16, 2009
Messages
6,908
My 1996 Buick Roadmaster with 244,000 miles and always used Castrol GTX petroleum oil, but with synthetic oil prices coming down I'll strongly considering changing to synthetic....any ideas or reasons why this wouldn't be good for this old 350 V8 LT-1? Would welcome any thoughts or experiences on this before I make the change...
 

GA_Boater

Honorary Moderator Emeritus
Joined
May 24, 2011
Messages
49,038
I always heard that switching to synthetic on high mileage motor started seal leaks. Maybe newer blends are better or there are high-mileage versions now. :noidea:

I don't have any experience with older vehicles and syn oil. And Googling is simply confusing!
 

NYBo

Admiral
Joined
Oct 23, 2008
Messages
7,107
I always heard that switching to synthetic on high mileage motor started seal leaks.

Ancient history. No problem at all with switching. But what are you trying to accomplish, robert? You will get better protection under severe conditions like towing, but it's no magic potion.
 

82rude

Rear Admiral
Joined
May 8, 2012
Messages
4,082
Soon as ive used up my free oil changes at ford for my edge I will be switching to syn for the life of the suv.Maybe I can pay the diff and go syn right away,maybe.17 bucks for 5 quarts of supertech full syn (warren oil).Go for it Robert.
 

poconojoe

Lieutenant Commander
Joined
Sep 10, 2010
Messages
1,966
I'm no expert, but I had an f250 years ago (4.9L straight six) that didn't have anywhere near that high mileage as you stated. I can't remember the mileage, but it was way well under 100,000. I switched to synthetic and my oil pressure gauge went bonkers. I was told that synthetic oils had better cleaning abilities and all the crud in an engine can break loose and create problems.

Now I don't know if that was correct or if things have changed, but if my car had that many miles on it, I wouldn't change a thing. With all those miles, I'd leave well enough alone. But that's me...
 

robert graham

Admiral
Joined
Apr 16, 2009
Messages
6,908
Ancient history. No problem at all with switching. But what are you trying to accomplish, robert? You will get better protection under severe conditions like towing, but it's no magic potion.

Not really trying to accomplish anything, but have assumed the synthetic was better oil, and only reason for not changing so far has been price of synthetic oils being a good bit higher. Seems like the prices have come down to the point that I should just make a choice. The specific synthetic I'm considering is the Walmart Supertech which costs about $15 for 5 quarts. I plan to continue changing my oil every 2 or 3 thousand miles either way....I just don't like dark/black oil in my engine.
 

southkogs

Moderator
Staff member
Joined
Jul 7, 2010
Messages
14,785
I'm no expert, but I've been driving older cars all my life (just don't like spending the money on new cars). I have only had two vehicles that didn't make 200k before I got rid of 'em, and have had several go to 300k and up. My routine on all of 'em have been the same: oil change every 4k - 6k miles, get the right viscosity according to the manufacturer recommendations of whatever is on sale that week at the parts store.

I've kinda' hit the point where I really don't think much matters beyond keeping it regularly changed.
 

bigdee

Commander
Joined
Jul 27, 2006
Messages
2,665
....I just don't like dark/black oil in my engine.

Thats coming from 244k miles of wear and blowby. Synthetic is not going to change that. If you still plan to change every 2-3 thousand miles your not saving money. That tired old Buick will meet its same death date whether syn or dino.
 

JoLin

Vice Admiral
Joined
Aug 18, 2007
Messages
5,146
I was told that synthetic oils had better cleaning abilities and all the crud in an engine can break loose and create problems.

That's the same old wives' tale that was told when "detergent" dino oils started to become popular (that was pre-synthetic and yes, I'm that old). In truth, the crud never "broke off"- it very gradually wore away.

Virtually all motor oils (dino and syn) have been loaded with detergents for many years. Any engine given even semi-regular changes will be clean as a whistle on the inside.

My .02
 

crazy charlie

Vice Admiral
Joined
May 22, 2003
Messages
5,352
DONT DO IT!!! BEEN THERE...DONE THAT I had same mind set with 100k MINT Jeep.Couple days after the syn oil change oil leaking severely.Quick research stated that the synthetic oil did not have the same gasket "plumping " qualities as conventional oils .Changed it out to conventional immediately and it slowed leak but had some leak from then on.I only recommend use of synthetic on new engines.Conventional oil has served your engine well so far....WHY change. Charlie
 

poconojoe

Lieutenant Commander
Joined
Sep 10, 2010
Messages
1,966
Opinions on this seem night and day. I wouldn't want to disagree with anyone's experience or opinion. That being said, if it were me, I'd leave well enough alone. As someone stated, you're gonna keep changing the oil at your previous consistent intervals, so why bother converting to synthetic. Obviously not for its longevity.
 

82rude

Rear Admiral
Joined
May 8, 2012
Messages
4,082
If you are waffling on syn oil maybe consider a oil formulated for high milers.You could also use synth oil and just change the filter 1/2 way making sure to add some to the new filter also or just top it up.
 

dolluper

Captain
Joined
Jul 19, 2004
Messages
3,900
Where's lube dude... Anyways high milage oil has less detergent. So more sludge stays keeping the bucket together. My advise is keep using the same as you have being using or replace one quart (litre) with straight 30 or maybe know as non detergent 30
 

bigdee

Commander
Joined
Jul 27, 2006
Messages
2,665
Make life simple, let your wallet chose the best price API certified oil at the correct viscosity and call it a day. Life is too short to worry about an engine with 244k miles on it. I had an old ford van with almost 200k miles on it when I bought it. It was a beater and I did not want to spend much money on it. I had access to USED hydraulic oil from an industrial plant so I used that old oil whenever I changed or added oil. Van had almost 300k and still running when I got rid of it!
 

robert graham

Admiral
Joined
Apr 16, 2009
Messages
6,908
Just to clarify, the oil never gets even close to dirty, as for years I've used motor flush at oil changes about every other change. I use Castrol High Mileage GTX oil. Just considering the change to the Supertech High Mileage Synthetic oil. And I also add a quart of Lucas Oil Leak Stop at every oil change to help the seals and especially valve stem seals that can sometimes get weak at high miles....so far, no oil burning or smoking...This change to synthetic seems controversial and debatable but guess I'll go with the consensus, whichever it is....
 

robert graham

Admiral
Joined
Apr 16, 2009
Messages
6,908
Just to clarify, the oil never gets even close to dirty, as for years I've used motor flush at oil changes about every other change. I use Castrol High Mileage GTX oil. Just considering the change to the Supertech High Mileage Synthetic oil. And I also add a quart of Lucas Oil Leak Stop at every oil change to help the seals and especially valve stem seals that can sometimes get weak at high miles....so far, no oil burning or smoking...This change to synthetic seems controversial and debatable but guess I'll go with the consensus, whichever it is....p
 

harringtondav

Commander
Joined
May 26, 2018
Messages
2,438
I swear by syn lubes, and apparently auto mfgs also do, since it's stenciled onto my engine oil caps. But I believe the benefit starts at the get-go. A '96 vehicle engine seals/gaskets could handle syn. I used it in two oldies w/no problems, and good engine longevity evidenced by low oil consumption at high miles.

But if you '96 consumes excessive oil, switching to syn will just consume more expensive oil. But if the consumption is moderate, < 1 qt/ oil change, I don't see a problem switching to syn. It won't reverse any wear, but it will slow down future wear.
 

ezbtr

Commander
Joined
May 1, 2002
Messages
2,954
I wouldnt, just not worth it at those miles, keep doing what you've been doing ;)
 

robert graham

Admiral
Joined
Apr 16, 2009
Messages
6,908
Well, I changed my oil this week...4 quarts Supertech High Mileage 5W30 Synthetic and a quart of Lucas Oil Stop Leak....I'll be pulling the boat to Florida next week, so guess we'll see if anything good or bad happens during this 1000 mile trip....will let you know what happens...if anything..
 
Top