mightyhye

Just wondering what you guys think about switching from castrol 10w-30 to mobil 1 or any other synthetic on a 1992 V6 4x4 pickup with 159,000 miles on it. Engine had a full rebuild at 138,000 miles. I've switched over to synthetic in other older cars before and gotten leaks due to synthetic being more viscus.

-Shawn

jimbo74

if there are no leaks now, there wont be any with a switch to synthetic.....

Silver_Truck

not necesarily, alot of people have had leaks when switching to synthetic. I would go for it though I switched at 390,000 and haven't had any leaks

jimbo74

its an old wives tale..... synthetics are made so well now that there is special stuff in them that compensates for it being so pure and still allows the seals to swell up and not leak

ChickenLover

I never had a leak until I switched to synthetic at 86k. The rear main seal would leak like crazy when the engine was under heavy load in the heat. I switched back to dyno and she never leaked again. I recommend sticking with regular oil.

marko3xl3

It all depends, sometimes you are lucky, sometimes you aren't; it also depends on which sythetic brand. As it is true that the additives being put into synthetics do help, it's the nature of the beast for synthetic oils to be thinner (smaller particles) which manage to flow past engine 'holes' much easier. Especially in older engines, where dino oil has already plugged up most of the holes (it might have caused ), synthetics have a tendency to break up that sludge and protrude through where that dino sludge used to be. To avoid any surprises later on, run your engine on very thin "flush" synthetics and then fill it up with your every-day use synthetic just in.

Anyways, I have just converted to synthetics from (AFAIK) 117k of dino oil use, and believe it or not, NO LEAKS WHATSOEVER. I filled the crankcase with 6 quarts of Mobil 1 10W-30 (which is over spec, but just barely reached the tip of the stick) and now, about 2 months and 3000 miles later, it is going over the tip of the stick instead of leaking. Weird eh? Next I am going to try and use 5W-30 to see if that will leak, as 10W-30 is too thick for the winter.

mightyhye

thanks for the reply everyone. I'm gonna have to think about it some more and find out from the prvious owner just what seals and gaskets were replaced during the rebuild before I make the change. If anyone else has experience with switching from dino oils to any of the synthetics, I would love to hear about it.

-shawn

2ToyGuy

I did it, I admit it, I went synth. At about 80k on the 4Runner, and at 100k on the p/u. I didn't get any new leaks. The old ones didn't get any worse, either. I try to stay on top of any leaks that pop up, and it seems to me like it's mostly the valve cover gasket or the rear halfmoon on same. I just slap a new one on, and voila`, no more leak... I also changed my bikes over when I bought them, and the police bike had over 100k on it when I did it, and no leaks at all. That was a HECK of a bike! It sure seemed to make them run more smoothly, and much, much cooler. I went and bought a new filter one day for my Virago, it was over 105 out, and when I got home I was able to change the oil without burning myself in the least.
To my admittedly untrained ear, both my trucks ran smoother and more quietly after I switched. And it seemed to me that whenever I needed to take the valve cover off, or in the case of the 4Runner, the head, whatever, things looked cleaner. Once again, a strictly subjective observation. And, when I did a "slickness test"; getting a little on my fingers and then wiping as hard as I could with a cloth, my fingers were still very slippery. And that was with oil I had just drained during a scheduled oil change.
So, there're my experiences and opinions on synthetic...Castrol Syntec 20W50, BTW. I use that weight due to the heat down here. Heck, our winter lows are higher than a lot of places summer highs...

marko3xl3

20W50 I would think that's good in the summer (even though I wouldn't go that high). What do you use in the winter?

2ToyGuy

Same. I change it every 3k, but always use the same weight, winter or summer. It may be a bit high for winter, but I've seen over 90* in the dead of winter here, so...