Running Synthetic in a older high mileage engine?

[adventureduo]

Can you guys school me on this topic?

So as some of you know, my buddy is now a vendor for AMSOIL and he is supplying us with fluids for our rig. As most of you also know.. they only make synthetic lubricants.

My question is... how do you guys feel about switching over to synthetic on a high mileage motor? I've heard so many different things, i dont know what to believe anymore. The seals will leak now if i switch over?.. the oil burns cleaner and i'll have to change it every 2k-3k miles to 'train' the engine? It will be fine. It will burn oil like a madman.. I've heard so many different views.. im really lost. I talked to my long time mechanic on Friday and he said that he wouldn't do it. That basically.. got me thinking.

Well, what do you guys think? Should i just leave it be and keep running the old regular motor oil?

Side note: He's offering me the extended life/high mileage synthetic by the way. And i have a 185k miles on our 1993 FZJ80 4.5 liter.

Any input on this would be greatly appreciated.

 

[bigreen505]

I switched the Pathfinder to Valvoline High Mileage dino oil at about 275,000 mi and it just made a mess on many different levels. I switched to synthetic 5w-30 at 300,000 and 0w-30 at about 315,000 and the engine has never been happier. On dino oil, including the high mileage stuff, I would burn about a quart or so every 3,000 miles. On the synthetic I burned about a half-quart every 5,000. To switch over I ran a can of engine flush (the thin oil, not the kerosene). I did the first change at 5,000 and then 10,000 after that.

Based on limited personal experience, I'm not sold on any high-mileage additives, just high quality synthetics everywhere except hydraulic fluids.

 

[DaveInDenver]

I ran Syntec in my truck and will again after I break in the new engine. BTW, the engine work has nothing to do with synthetic, I broke a timing chain which is most likely due to the piece of junk aftermarket parts. The only reason you don't want to run a modern synthetic is if your engine is in such poor shape that it actually leaks a lot of oil currently and that's only because synthetic is too expensive to let pool on the ground. If the engine is in good shape, decent seals and condition, synthetic isn't going to hurt anything and will only help. My truck was at ~200K when the timing stuff went and showed no signs of problems with the syn stuff.

 

[adventureduo]

Great responses! keep em coming please!

 

[Jonathan Hanson]

In my original F engine in the FJ40, I switched from Castrol GTX to Castrol Syntec at around 200,000 miles. No dramas, no leaks, no magic differences in power or fuel economy, but I felt like I was treating the engine a bit better.

 

[Skillet]

Great responses! keep em coming please!

Immediately put Mobil 1 full synthetic in the 80 when I got it and it had 183k on the ticker. To the best of my knowledge, it had only used dino before that.

Runs beautifully for 27K so far.

Had a Blackstone test on the last batch with 6k on it and they said the oil could have gone to 12K.

When I first switched, it ate up oil at a fair pace but after the first 3K, that diminished.

Honestly, you cannot go wrong changing to full synthetic.

There are a lot of write-ups about it on mud if you want to poke around in the tech sections for your specific vehicle.

My .02

 

[RAM5500 CAMPERTHING]

Immediately put Mobil 1 full synthetic in the 80 when I got it and it had 183k on the ticker. To the best of my knowledge, it had only used dino before that.

Runs beautifully for 27K so far.

Had a Blackstone test on the last batch with 6k on it and they said the oil could have gone to 12K.

When I first switched, it ate up oil at a fair pace but after the first 3K, that diminished.

Honestly, you cannot go wrong changing to full synthetic.

My Experience Mirrors Skillets Exactly! Blackstone actually commented on how good mine looked!

Mine was switched at 118k and was dirty as hell at the first changed, now comes out very clean at 135k +/-

 

[cruiser guy]

IF the price on the synthetic is comparable to dino then use it, otherwise why change something that works well.

I've had synthetic in my 3B when it had 400,000 or so on it and it didn't seem to make a difference. Now the drive train is different, I'm convinced that synthetic there is worth while (I noticed a mileage improvement) and I have my own stash here in Central America because it is hard to find it here.

 

[adventureduo]

Thanks all. I will take your advice and go for it. The case of oil should be here any day now. Thanks again for your real-world experience responses. You set my mind at ease.

 

[pnwadventurer]

About 4000 miles ago, I changed over to 0-40 Mobil 1 on my 3FE powered Land Cruiser with now 185,000 plus miles. No leaks, no consumption yet.

It was probably not needed, but I changed the oil filter at the factory recommended interval of 3750 miles for severe service. I now need to figure out how many miles I can run before an oil change.

Steve

 

[7wt]

While I didn't have the major miles that others had, I switch to synthetic and won't go back. Nowing that I can put 10,000 miles on a oil change is very comforting although I change it at 5,000. All my stuff, diffs, transfer case and tranny are all Mobile1 and I couldn't be happier. It's in the wifes Crand Cherokee as well. Since you are getting an inside deal on the Amsoil, I say go for it! Switch it all over to synthetic. I just wishe Mobil1 would come out with synthetic gas!!!

 

[cruiser guy]

Just a quick comment. In my case I'm running a diesel and an extended drain interval in a diesel is not a good idea due to soot buildup in the oil. That's one of the reasons I don't do synthetic in my engine but I still use it everywhere else.

 

[dieselcruiserhead]

It makes worlds of difference in cold weather. If you have no small leaks I would say run it.. There are some interesting studies on turbo diesel register about extended intervals with diesels. Some guys have as many as 50K miles on their amsoil and purple (forget the name), sending in oil samples for analysis every 5-10K miles, and no problems..

I run it in my higher mileage Saab as well. Not sure if it ran dyno or not before but it runs great and also no oil loss. I run about 10-12K intervals usually..

 

[mike h]

I've been thinking about it just for the longer change intervals - dropping my skids is a PITA, and it means I can never use a JiffyLube on the road.

I ran Amsoil in an older Quattro and did experience seal seep, and synthetic in the gear box made the shifter feel notchy; the fluid was so much thinner than dino. The Quattro was short-lived love affair for me so I can't give a longterm report. My mechanic at the time was a synthetic preacher, and I'venever heard anything against using it.

If I were to swith my 97 Nissan w/ 120k to synth this season, is there a 'flush' recomendation? Such as run put in synth for 1000 miles, and drain/fill, then go the 5000?

the seals are tight on the Nissan, and knowing how improved tolerances are now I'm not concerned with seal seepage, although my 3 months of subzero may prove otherwise.

m .

 

[cruiser guy]

There are some interesting studies on turbo diesel register about extended intervals with diesels. Some guys have as many as 50K miles on their amsoil and purple (forget the name), sending in oil samples for analysis every 5-10K miles, and no problems.

The other brand you are talking about is Royal Purple I think. Extended drain intervals work if there is an oil lab nearby but by the time you've taken a sample you may as well just change the oil.

Sampling is $15 more or less. For me thats about the cost of the oil and filter. The work isn't too much different. You still need to go and get all dirty.