I'd never run less than a 10Wanything unless I had to. Synth or otherwise.
I've got about 240K on my 22re in my 88 and using 10w30 synth resulted in a rather significant leak in my front oil seal, which didn't leak with 10w40 dino... go figure... and over about 3000 miles total, replacing lost oil with 10W40 Rotella, the leak stopped... guess no more synth to leak around the seal?

Just a warning. Be prepared.

 

x2

The molecules that extend the viscosity of an oil can only make it act thicker - in other words, a 10W30 is a 10 weight oil, and a 10W40 is a 10 weight oil with more viscosity index improvers. As the VIIs break down, the oil reverts to its natural state, the lower number. 5 weight oils are too thin for our engines during the summer or in a region with a mild winter, imo, but they may be a good choice for very cold winters since heavier oils don't flow well in very cold temps. That's one area though where true synthetic oils really outshine the dino oils - they flow much better at colder temps, so a 10W30 Amsoil or Mobil 1 will probably flow as well or better at 0 deg F as a 5W30 dino and will provide much better lubrication.

BTW, the VIIs make an oil act thicker only for purposes of creating an oil film that will cling - they don't give the oil the superior lubricating qualities of the heavier weight oil. They just keep the lighter weight oil in place.

In the 3vze, I recommend running 10W40 in the summer and 10W30 in the winter, unless your winter temps get below 0 deg F, in which case 5W30 would be better. When I lived in New Mexico I ran 20W50 in my veezy during the summer with no problems.

I have always used Castrol Syntec (since I bought the truck at 107k miles), which is a "Group III" synthetic oil: it's a "hydro-cracked" oil created from petroleum base stock, so it's not considered a "true" synthetic. (Valvoline SynPower & Penzoil Platinum are similar.) Syntec is still a very good oil - about the highest quality of the petroleum-based stuff, but its expensive for what it is, especially lately.

The one time I used Mobil 1, a Group IV PAO (polyalphaolefin) true synthetic oil, it caused the form in place gasket sealing the oil pan to start hemorrhaging oil like crazy. What an unbelievable pain in the nether regions that was! I will NEVER use that stuff in my engine again, I don't care what anybody says. Maybe a different synthetic would work fine but I don't dare try. If I were to try, it would probably be Red Line since the type of synthetic oil they make (Group V polyol ester base stock) is chemically related to the stuff used in high-mileage oil that softens and rejuvenates dry seals. Amsoil is chemically the same as Mobil 1: a Group IV PAO; still, I know many of you use it with no problems, so it's probably a good choice. Maybe it has better seal-preserving additives than the Mobil 1. Royal Purple is often trashed as a poor-quality product on the excellent bobistheoilguy.com forum, but I know it too has its adherents. I've heard good things about Rotella, but don't know anything about it.

I believe synthetic blend oils never contain more than 30% synthetic.

When I changed my head gaskets at 218k miles after running Syntec for the previous 111 miles, I found the original cross-hatching still in the cyl walls, nice and even. Now at 281k miles, the motor still does not burn oil, so I'm happy with the Syntec.

 

You guys aren't making this easy... It's supposed to be a unanimous decision!

Thanks for the responses although I'm not sure how I should make this decisions for myself. Is there anything I can do to my truck that will help me determine if switching to Synthetic is a bad idea?

Such as running a compression test, inspecting part A, B, or C, etc...

 

LOL. Unanimous opinion about motor oil? Good luck. It's as bad as antifreeze choices. Probably doing what you're doing - asking for opinions and hearing what works for other people - is about the best you can do.

I think the best guide for determining the risk of oil leaks with synthetic will be the number of miles on your seals. Over 200k, true synthetic will be fairly risky, but a group III like Syntec, Synpower or Penzoil Platinum would probably be a good choice. As mentioned, Rotella has a very good rep too. If you really want to run a true synthetic, try Red Line.

 

hah! there will NEVER be a unanimous decision on oils. but after reading the posts that came in after my earlier one, i see a consensus as such:

10w40 in summer, 10w30 in winter 5w30 in extreme cold areas, full synthetic is just too "slippery" for our old engines and increases leakage.

and a couple peeps indicated using a "high mileage" style, which includes additives to swell some seals.

p.s. that rotella T is a good diesel oil, and a decent cheap alternative for cycles as long as you don't mind doing changes at dino intervals (3500mi) vs. synth intervals (6000mi). the rotella T does not have friction modifiers that standard auto motor oil has, so you can use it with wet clutches and not have slippage. but i would not recommend exceeding 3500mi. my bike would "tell me" when that oil was due for replace. i switched back to a synth cycle oil and my bike seems happier, shifting feels much better, less clunk. so much for cheapskatin'.
but i wouldn't use it in my truck. why eliminate the tech advances of oil for the last 20 yrs switching back to such a basic oil?

 

It will clean your engine not sludge it, diesel oil has alot of detergents and suspension agents to hold dirt when it gets into the oil. However diesel oil isnt good for your catylitic converter -- but from info on bobistheoilguy.com very few people have had clogged cats from diesel oil.

 

I didn't really expect to get everyone to agree...

So let me pose this question. If I do the synthetic and she leaks a whole bunch what's my recovery plan at that point?

 

Drain the synthetic, replace with high-mileage oil and cross your fingers. After 3-4 thousand miles, anything still leaking will probably need to be repaired. Seals probably will come back to where they were. My oil pan's fipg did not, and had to be replaced.

 

I was also thinking about switching to synthetic oil on my 22r but was unsure about the weight, so i thought i would ask you guys now.

What brand and grade of synthec would you recommend for a rebuilt 22r? It has about 2 years or less since rebuild and i mostly use it to go to school. Since the rebuild I have only used Castrol gtx 20w50, because that was the grade of oil in it when i got it. I, also understand it depends on temperature, and im located in virginia where it gets cold.

Also what fluids are better for the transmission, transfer case, and diffs? Thanks

 

I pulled my oil pan a couple days ago swapping it on to a new long block. No sludge. Not even a little bit. I was amazed, the motor had 250k on it and blew a headgasket due to overheating (not the oil's fault)

I ran it in my motorcycle because it supposedly plays nice with the wet clutch and can perform well when dirty.

 

OK that does it, as an experiment i am going over to Castrol Syntec 10/30 or 40. I have had a bit of a main seal drip for years (5 or 6) now, we will see what happens.

 

I know last post over a month ago , but what the heck.

 

I run 5w30 year round. 5w30 is ALWAYS a better choice than 10w. MOST engine wear occurs at start-up. You WANT a thin oil at start-up so it pumps through the system quickly and easily. At operating temperature, 5w30 is the same viscosity as 10w30. There's no benefit to running the 10w over the 5w.

 

Well i made it to 280k with 10, i'll stick with it, ah but sound advice, thank you.

 

Some good info on Oil

http://www.carcraft.com/techarticles...oil/index.html

 

If you want to learn pretty much all you care to about oil: http://www.bobistheoilguy.com/

 

Cool thanks Shaeff.

 

What about high mileage 22R?
what motor oil they need for winter and summer?

 

how many miles did you have a that time?

 

167k, and it was 1998, so the truck was 9 years old. I've since learned that the Mobil 1 formulation has changed since then and it is no longer an all-PAO basestock, but that it now contains cheaper group III basestock which is the not-a-true-synthetic oil refined from petroleum. And since Mobil refuses to divulge how much of Mobil 1 is now a group III, I think the safe assumption is that it makes up a majority of the product. So while that is bad (imo) from a product quality and value standpoint (also from a typical corporate lie and cheat you out of your money standpoint), it may mean that the current Mobil 1 product would not have caused the leak.

Also, I don't know and never will why exactly Mobil 1 caused that leak in the pan fipg. Did it dry and shrink the gasket material or just wash some gunk out of the way. I suspect it was the former, but that's just a guess. At any rate, that was 11 years ago, and synthetic oil formulations have improved, with higher amounts of shmesters, so I think the only way they would cause leaks now would be by washing away gunk that may be sealing an existing leak.