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

[Boston Mangler]

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