10-w40? dino or syn?

[1984 CJ7]

Getting ready to change it and I think 10w40 would be bet for summer driving here in the PNW. Also, goingto change to Royal Purple syncromesh.

 

[elwood blues]

If your engine has never been rebuilt, I would be hesitant to change over to a full synthetic oil, if you're not leaking oil now, you may start.

A long time ago, I worked as a mechanic and saw this when synthetic oil first came on the market, everyone wanted to go to synthetic, the only thing is, all of those old engine with semi worn out gaskets aren't used to synthetic oil, you may start to develop leaks from places.

Now, I'm not telling you not to switch over, use whatever oil you want to, just know that I have seen older engine that didn't leak, or leak much, start leaking when they are changed over to synthetic. Just my 2¢.

 

[Saddle Tramp]

I agree about the synthetic. Older worn motors tend to leak that stuff. In the day we used either 10w – 40w or just a straight 30w.

 

[1984 CJ7]

Perfect, I will stick to Dino 10-w40. Saves me money anyway!

 

[elwood blues]

Perfect, I will stick to Dino 10-w40. Saves me money anyway!

 

[007]

I agree with the above, and I'd also recommend a quart of Lucas Oil Stabilizer as well. Really helps hold the viscosity and reduces wear. These engines can run a little warm and this stuff really does work.

 

[dauntless89]

I keep oil in mine, and it keeps runnin'...

My preference is Mobil Delvac. 10w-30 if you can find it but 15w-40 (more common) won't hurt an older engine, especially with higher miles. The 4.0 in my wife's XJ seems to run quieter and smoother with it.

I live in a small town in the middle of nothing and I have to run about a half hour on the highway to get to anything. My oil lasts a long time since the engine always gets good and hot, thoroughly cooking out all the nasties and water that tends to ruin your oil. I change filters around every 5k, and would change oil every 10k but all of my rigs leak enough that I don't bother to change it.

I wouldn't run the heavier Delvac in a newer-design engine though. I tried it in my wife's 97 Subaru (calls for 5w-20 I think) and the valves got noisy enough I actually drained the brand new oil out and put some of the correct weight in. It seems like the engines they've designed in the last 20 years really are picky about oil weight being correct, whereas it seems like every SBC I've had, the straight six in the XJ, the Buick 225 in my CJ, and the 22r in my pickup (most all designed in the 50s) are quite happy to run whatever the hell oil you put in them.

Truth be told, I actually save most of my used oil, run it through a fine filter, and use it to keep the 22r topped off. That truck gets between 15 and 20k a year put on it, almost all highway, uses about a quart and a half a month. I had it apart for a head gasket last month, and ended up dropping the pan to fish out some pieces of the cam chain tensioner and there was almost no sludge or sediment. Pretty cool I thought.

Anyway... there's a lot of undue hype about "which oil is better."