switch to synthetic? - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

91CRXsiR · 06-18-2002, 01:31 AM

my 89 fastback needs a oil change soon. its been running on normal oil its whole life im guessing...

i heard its bad to switch to syn oil when it hasn't been runnig on it? or theres som breaking in period like that..

is any of this true? if so what oil should i use? 10W-30?

blink0r · 06-18-2002, 02:06 AM

What you've heard is true. On an old engine, don't switch to synthetic. Stick to the regular oil that you're using now. If anyone tells you otherwise, they're an idiot!

guidot · 06-18-2002, 03:57 AM

If you are using regular oil, stick to it.  I use Castrol GTX 10W-30.  The synthetic oil will shrink the seals in the engine, probably making bigger gaps than there are now.  This is bad.  Supposedly, Valvoline MaxLife oil is supposed to expand the seals in the engine, but is really only meant for cars with seals that are shrunk, I think (aka leaking oil).

pete north · 06-18-2002, 09:29 AM

Where does all this come from?

I have yet to see proof that a Synthetic such as Mobil 1 causes seals to shrink. The only evidence I have contradicts this.

I see no disadvantage to using Synthetics (besides cost).

They give superior protection against viscosity breakdown. Thats ALWAYS a good thing.

91CRXsiR · 06-18-2002, 03:16 PM

thats true but supposedly if the car ran w/ reg oil it would be bad to switch to syn..

but what about SRs? would they benefit from syn oil?

i know honda owners swear by the stuff..

pete north · 06-18-2002, 03:38 PM

I think all that about putting synthetic in an engine that's been run with conventional oil before is a crock.

If I had an SR20DET I wouldn't run anything but Mobil 1 10W-30 or maybe even 15W-50 if I was doing hard driving or if I lived where it gets really hot.

The reasons I would use Mobil 1 in an SR:

1) Lower friction means less heat and less wear

2) Superior resistance to viscosity breakdown, which is key in any high-revving engine. The fact that its also lubricating a turbo thats spinning at over 100,000rpm means resistance to viscosity breakdown is even more important.

3) Superior resistance to thermal breakdown because that turbo gets damn hot. Nevermind the rest of the engine...

So, personally if I had an SR20DET in my 240, I'd be running Mobil 1 for sure. Again, I don't buy the stories about Mobil 1 shrinking seals.

Natty · 06-18-2002, 03:49 PM

Well, here is the problem. If you have old seals and the engine has always run organic oil, and then you run syn, it may leak. This is because from what I have been told, the syn can leak through smaller imperfections in the old seals.
I am sticking with Castrol GTX for my old ass KA.
Jeff

06-18-2002, 02:06 AM	#2
blink0r Zilvia Junkie Join Date: Mar 2002 Posts: 329 Trader Rating: (0) Feedback Score: 0 reviews	What you've heard is true. On an old engine, don't switch to synthetic. Stick to the regular oil that you're using now. If anyone tells you otherwise, they're an idiot! __________________ 1991 Nissan 240sx SE "Friends don't let friends drive trucks."

06-18-2002, 03:57 AM	#3
guidot Zilvia Junkie Join Date: Feb 2002 Location: Cape Cod, MA Age: 45 Posts: 443 Trader Rating: (0) Feedback Score: 0 reviews	If you are using regular oil, stick to it.  I use Castrol GTX 10W-30.  The synthetic oil will shrink the seals in the engine, probably making bigger gaps than there are now.  This is bad.  Supposedly, Valvoline MaxLife oil is supposed to expand the seals in the engine, but is really only meant for cars with seals that are shrunk, I think (aka leaking oil). __________________ -Jeff T. 96 240SX 240SXONE http://www.240sxone.com

06-18-2002, 03:49 PM	#7
Natty Zilvia Addict Join Date: Dec 2001 Location: Nashville, TN Posts: 944 Trader Rating: (0) Feedback Score: 0 reviews	Well, here is the problem. If you have old seals and the engine has always run organic oil, and then you run syn, it may leak. This is because from what I have been told, the syn can leak through smaller imperfections in the old seals. I am sticking with Castrol GTX for my old ass KA. Jeff __________________ 1991 White 240sx Fastback LE, rusty spoiler, weak driveshaft, exhaust rattle.... Rattles are just your cars way of saying 'I love you.'

06-18-2002, 01:31 AM	#1
91CRXsiR Nissanaholic! Join Date: Oct 2001 Location: City of Industry, CA [626] Age: 42 Posts: 2,092 Trader Rating: (1) Feedback Score: 1 reviews	my 89 fastback needs a oil change soon. its been running on normal oil its whole life im guessing... i heard its bad to switch to syn oil when it hasn't been runnig on it? or theres som breaking in period like that.. is any of this true? if so what oil should i use? 10W-30?

06-18-2002, 09:29 AM	#4
pete north Join Date: Mar 2002 Posts: 39 Trader Rating: (0) Feedback Score: 0 reviews	Where does all this come from? I have yet to see proof that a Synthetic such as Mobil 1 causes seals to shrink. The only evidence I have contradicts this. I see no disadvantage to using Synthetics (besides cost). They give superior protection against viscosity breakdown. Thats ALWAYS a good thing.

06-18-2002, 03:16 PM	#5
91CRXsiR Nissanaholic! Join Date: Oct 2001 Location: City of Industry, CA [626] Age: 42 Posts: 2,092 Trader Rating: (1) Feedback Score: 1 reviews	thats true but supposedly if the car ran w/ reg oil it would be bad to switch to syn.. but what about SRs? would they benefit from syn oil? i know honda owners swear by the stuff..

06-18-2002, 03:38 PM	#6
pete north Join Date: Mar 2002 Posts: 39 Trader Rating: (0) Feedback Score: 0 reviews	I think all that about putting synthetic in an engine that's been run with conventional oil before is a crock. If I had an SR20DET I wouldn't run anything but Mobil 1 10W-30 or maybe even 15W-50 if I was doing hard driving or if I lived where it gets really hot. The reasons I would use Mobil 1 in an SR: 1) Lower friction means less heat and less wear 2) Superior resistance to viscosity breakdown, which is key in any high-revving engine. The fact that its also lubricating a turbo thats spinning at over 100,000rpm means resistance to viscosity breakdown is even more important. 3) Superior resistance to thermal breakdown because that turbo gets damn hot. Nevermind the rest of the engine... So, personally if I had an SR20DET in my 240, I'd be running Mobil 1 for sure. Again, I don't buy the stories about Mobil 1 shrinking seals.