switching to synthetic

[grandnat86]

i just purchased an 86 grand national wth 130,000 miles, everything is stock except for a hooker catback. the motor runs great but when i asked the owner what he used for oil he said 10w-30 conventional, would i be ok to switch to synthetic.

 

[LOLGN]

You'll get lots of differing opinions on this subject. I can't think of any legitimate reason not to switch to synthetic other than cost if don't have two nickels to spare. I'm switching the gn over to synthetic next weekend, but everything else I own has it in the engine/gearbox/trans/diffs etc.

 

[Nick Micale]

You'll get lots of differing opinions on this subject. I can't think of any legitimate reason not to switch to synthetic other than cost if don't have two nickels to spare. I'm switching the gn over to synthetic next weekend, but everything else I own has it in the engine/gearbox/trans/diffs etc.

In over 30 years working on and dealing with turbo Buicks, I have not found, or even heard, one "legitimate reason" verifying any benefit when switching to synthetic oil in this 1960's designed V-6?

Have seen many 150K+ turbo Buicks running well with the original, un-opened engine and original turbo that have always been operated with regular oil.

There are some downsides to synthetic oil other than cost, and one main one is it drains off bearings and cylinder walls in a few days of non-use. Conventional oil will stay in place to eliminate dry starts.

Just my opinion and experience, your $$$, so spend it as you see fit!

 

[Turbo6inKY]

i just purchased an 86 grand national wth 130,000 miles, everything is stock except for a hooker catback. the motor runs great but when i asked the owner what he used for oil he said 10w-30 conventional, would i be ok to switch to synthetic.

It'll be fine unless your engine leaks. Synthetic will make the leak worse. Use the 50w Mobil1, Royal Purple, or Amsoil so you get enough ZDDP, or throw a can of GM EOS into a normal fill of 10w30.

 

[DR BOOST]

In over 30 years working on and dealing with turbo Buicks, I have not found, or even heard, one "legitimate reason" verifying any benefit when switching to synthetic oil in this 1960's designed V-6?

Have seen many 150K+ turbo Buicks running well with the original, un-opened engine and original turbo that have always been operated with regular oil.

There are some downsides to synthetic oil other than cost, and one main one is it drains off bearings and cylinder walls in a few days of non-use. Conventional oil will stay in place to eliminate dry starts.

Just my opinion and experience, your $$$, so spend it as you see fit!

i agree. Nick is the third engine builder that i have heard say not to use synthetic. Although many others will say its ok to use , but they usually have very mild buildups. just use the regular stuff and change it often.

 

[Brer Rabbit]

Another perspective.

Last summer I directed a Turbo Buick owner to a friends shop to have his rear main seal replaced and a few other minor things. During the rear seal replacement the mechanic commented that the bearing on the rear main cap was in bad shape. (I didnt see it myself, but the mechanic knows his sh!t) The mentioned Turbo Buick owner bought the car new and has run Mobil 1 synthetic only. He even brought a case to put in after the work was done. I believe the car had around 60k miles on it. The car is adult driven never raced or thrashed ---bone stock. I think its safe to conclude that the Mobil 1 did not help this motor at all. Im not saying the same would not have occured on conventional oil but that example was enough to keep me away from synthetic oil unless its trans fluid or rear diff fluid.

 

[Roger]

I switched mine at 105k when I purchased it. Never an issue.

I switched my F at 200k in the late 60s & was told all the horror stories before I did the switch. Never an issue.

 

[Camfreek]

I don't know about that stuff!!!!

I have a 1988 Trans Am, nothing to wild, but everyone said after the break in period change it to synthetic!!! I did and that motor went down hill fast!! After have another one built to the smae specs and switching the oil over same thing, bad motor. The machine shop said it is the timing gears I am running are ruining the engine!! Funny Cause my brother has timing gears on his 5.slow and revs his alot high then mine and no problems there. Well long story short after 3 motors build all to the same specs 2 on synthetic that never saw past 10,000 miles and the one I am still running nw with well over 80,000 on plan old oil!!! Can't say the same for all cars, but I will never touch that stuff again, seems to cost way to much all the way around!!!!:biggrin:

 

[wickedtt]

Also I don't know if its true but they say once you switch to the synthetic you can't switch back to reg. dino oil

 

[Turbo6inKY]

Also I don't know if its true but they say once you switch to the synthetic you can't switch back to reg. dino oil

It's not true, they're both compatible with each other. You can switch back and forth all you want.

The failures described above cannot simply be blamed on oil. There's not enough information from what was posted to determine any cause of failure.

Correlation does not equal causation.

 

[smokinttype]

Its not worth the 5hp you might get. It will start leaking like all get out and you'll wish you never did it. I have never run it in anything that I have been a part of. You really dont want to do it with an engine with that many miles on it b/c the seals are already worn a bit. Just my .02