Just was wondering what opionions are. My '97 4.6L has 150,000 miles. It runs good, without any oil consumption. I've used Havoline 10W-30 since new with 3,000 mile changes. Last oil change I switched to 10W-30 Motorcraft syn. blend and now ready for the next oil change. I am thinking of going to what the manufacturer recomendations are, 5W-30 Motorcraft which is the 529 spec. and full synthetic.

My question is, with a 10 year old truck, how will the fully synthetic oil treat the seals that have never been exposed to a fully syn. oil? The last change with the syn. blend has not caused any leaks but I still don't want to cause any problems. The reason for the Motorcraft choice is that I can get it at a good price. Any problems with the switchover to fully synthetic?

 

So why switch? Whatever you're using now is obviously working pretty good, I'd leave it be.

 

I absolutely 100% agree w/ Quintin,if your truck is not using any oil w/ 150,000 miles on it,then why change? Keep using that oil,seem to be working just fine.

 

If you do want to switch, I don't see a problem - but can you get the 5W30 Motorcraft blend at a good price? Any 929 spec oil will work fine in your engine, and 929 does not require synthetic. If you change at 3000 miles, you really don't need a full synthetic.

I would think most synthetics these days that meet 929 spec would have seal conditioners to avoid problems. Back in the "old" days this was a problem though, you switch an old engine over from dino and you were asking for seal leaks big time.

 

Quintin is right in my opinion. You've gone this long with good maintenance, so why change?

I am a huge advocate of synthetics. The cost is just not an issue to me. However, with the mileage you have I personally do NOT recommend you change. A blend is only up to 30% synthetic.

I think you could cause problems going to a full synthetic now.

I screwed up a Nissan Pathfinder several years ago by switching to synthetic.

I ran Castrol 20w50 in it since it was new, and that was a great rig. I changed the oil every 2000 miles because I towed a trailer with 2 atvs on it all the time during hunting season and it went to many different states. Never ever had a problem.

At 120K miles, I found some Mobil 1 synthetic on sale, and I didn't know anything about the chemistries etc. I asked the guys at Napa if there would be a problem switching and I was told no.

So, I bought it and put it in. 2 days later, the motor was never the same. Too many symptoms to list, but I made a very poor decision based on ignorance. We donated the Pathfinder to Goodwill.

You've done things a little different. You've migrated from a dino to a blend, and now thinking of going full synthetic. If you decide to go forth, then I'd recommend buying MC blend and a few quarts of their synthetic in the same wt., and mix them for a couple of oil changes, then go full synthetic. Only time will tell if your seals begin to fail.

 

Thanks for the good info guys. I'll probably keep things as is. I just want to take the best care possible without messing things up.

 

My '97 4.6L is still running strong on nothing but Havoline 10W-30 and 5K mile oil changes. Synthetic is better oil, but these engines run rather cool and probably don't benefit all that much from the extra protection.

I would also suggest not to change over to synthetic in an older vehicle that has been using Dino oil. The only oil consumption problems I've had in the last 15 years were on my Ranger & Grand Cherokee after just 1500-2000 miles running with full synthetic oil. Both didn't consume oil before the switch over to synthetic, and within a few months, they both started blowing smoke.

 

With that many miles on it, Id bet that your truck would burn or leak a little oil with synthetic.
I stick with a good 5w-30 dino oil. Im personally not a fan of Motorcraft oil because they switch suppliers on an almost yearly basis and you can never be sure who makes the oil for them.
I used Mobil Drive Clean and more recently Mobil Clean 5,000 and never had issues with it. Recently I switched to Castrol GTX 5w-30 becuase it has a higher rating than Mobil (SM, I think) and Ive been pleased with it. My truck has seemed to get better fuel economy since I switched to Castrol.

 

I think any SM oil is going to have some synthetic in it.