Really Stupid Question

[Kathleen2]

I have a really stupid question? Can you switch back and forth from regular oil to synthetic? I’m just wondering if there would be any harm to go back and forth. The reason I’m asking is that I have a case of Castrol GTX but there is a terrific sale for Castrol Synthetic.
Kathleen

[efusco]

In today's cars with today's oils it's OK to switch back and forth. In the past there were issues with doing that, but as I understand it those issues have been resolved.

[Charles Suitt]

Hmmm... Just an abstract question...

Why would someone WANT to switch back & forth from dino oil to synthetic?

[john1701a]

<div class='quotetop'>QUOTE(Charles Suitt @ May 10 2006, 10:55 AM) [snapback]252800[/snapback]</div>

Why would someone WANT to switch back & forth from dino oil to synthetic?
[/b]

That is an excellent question. Synthetic oil is a pretty darn cheap preventative maintenance thing you can do for your car, to the point of being trivial compared to most expenses. And it does provide a tiny MPG improvement anyway.

In other words, is saving that $12 to $15 really worth it?

[Walker1]

[quote=Kathleen2 @ May 10 2006, 11:27 AM) [snapback]252776[/snapback]</div>

I have a really stupid question? Can you switch back and forth from regular oil to synthetic? I’m just wondering if there would be any harm to go back and forth. The reason I’m asking is that I have a case of Castrol GTX but there is a terrific sale for Castrol Synthetic.
Kathleen
[/b]

It depends on money, personal pref, etc. I use full syn. oil in all my vehicles. I just put Mobil 1 in my 2006 Prius] 5,000 miles. It will remain in the engine until 30,ooo miles. I do this with all my vehicles. Haven't lost an engine or spent 10 cents on a mechanical problem yet- since about 1980. In my opinion, full syn. oil blows away any organic oil.

[aaf709]

I can think of one reason. I have synthetic in now, but if I discovered a case of dino oil in my garage (which I had gotten for my last car), I would want to use it up.

[Charles Suitt]

<_< Howdy aaf709

That case of oil... does it "happen" to be the correct viscosity? Seems unwise to risk an engine if it's not the recommended viscosity.

[aaf709]

<div class='quotetop'>QUOTE(Charles Suitt @ May 10 2006, 10:25 AM) [snapback]252881[/snapback]</div>

<_< Howdy aaf709

That case of oil... does it "happen" to be the correct viscosity? Seems unwise to risk an engine if it's not the recommended viscosity.
[/b]

For the sake of this discussion, let's say yes. That would make it a valid reason to go back to dino (and then back to synthetic when the case is used up), although that wouldn't happen all the time.

In my case, I did find a case, but as my wife's car uses that same viscosity, I'll use it there. Good thing to remember, though. I also found a case of straight 30W, which I gave to my father to take to the local Aerospace Museum where he volunteers. Someone there might need it.

[benighted]

I've heard that you aren't supposed to use synthetic if you have a higher mileage car that has only used dyno. Synthetic is thinner and won't protect as well in a worn motor (save maybe for high-mile formulations). In other words if you switch to dyno for a significant amount of time you might not want to switch back to synthetic but if you've only use synthetic in the car theres nothing to worry about because there is no extra wear caused by and requiring the thicker dyno oil.

[john1701a]

<div class='quotetop'>QUOTE(benighted @ May 10 2006, 12:40 PM) [snapback]252895[/snapback]</div>

Synthetic is thinner and won't protect as well[/b]

It will actually protect just fine.

The problem with a well worn engine late in life that has never used synthetic is the seals aren't that good anymore. So the thinner oil will leak out. That's bad (obviously).