Just wondering if the 5.4's are good enough engines to switch over to fully synthetic at 90,000. Regular oil was used up until the last two oil changes where I switched over to motorcraft semi synthetic oil. The engine has never used or dripped oil and is running good.

 

So why switch?

If it ain't broke, don't fix it.

I can't honestly say whether going to synthetic will cause any harm, since I believe every engine is a rule unto itself. But it's obvious whatever oil and filter you're using now is working well, so why not leave it be?

 

Yes.

Why do you want to use a synthetic now?

 

Gotta agree. FWIW, I 've always heard (through the rumor mill, not real experience) that switching to full syn in a motor with any sludge and stuff in it will actually start to clean away that stuff. And that's not a good thing. Once you ahve sludge or deposit build up, you want it to stay in place. Can start to clog stuff. Like I said though, just what I've always heard so take it with a grain of salt.

 

The reason I want to change is that Im a fan of synthetics and have used it in my supercrew since new. I believe it does keep your engine cleaner and will help make it last a lot longer. I want to switch because I had just bought my dad's Expedition after he went out and bought a new supercrew of his own. He always had the oil changed at 3000 miles with dino but now that I have it, I want to switch hoping I will get long(er) life from it. I was wanting to know if these engines are "tight" enough after the miles where it wont leak when the synthetics clean out the sludge. I may just stick with the motorcraft oil and filters on it from here on out.

 

ive heard the same thing. if you have any worn seals etc... synthetic will find a way to leak. i have 130k on my 97. im just gonna keep regular oil. i have no leaks so... wanns keep it that way.

 

If you have bad seals...

I have a '97 that had 86,000 on it last year. It always got dino it's whole life.

I did one change using the castrol synblend. Then I put some engine flush in it at the next change and went straight to synthetic. No Problems.

I always use Mobil1 5w30 and a Wix Filter

 

I agree with the motor flush.

I changed over 2 Toyotas each with 80K miles but the dino had always been changed every 2500 in summer and 2K in winter.

I used the Amsoil flush as directed in both. Allegedly the Amsoil flush has little to no kerosene.

Both Toyotas run perfect, with no apparent reactions to sludge, and both are using full synthetic. 1 is with Amsoil, the other uses Mobil 1 EP. Not one leak.

With all of the literature on synthetics, I influenced a guy I know in TX to change his truck over to synthetic at 110K miles. He also used the Amsoil flush as directed. He drives an F250 and has reported nothing out of the ordinary, including no leaks. He related to me that he has since put 20+K miles on the truck since the switch. So who knows, some rigs may leak, others may not. I think it really depends on the history of the motor. Good maintenance is always a great segway to switching to a synthetic. Poor maintenance with dino could lead to a lot of surprises, like a moderate leak on your driveway.

 

Change to "synthetic" at any time you like and don't worry about the seals. You're going to be hard pressed to find a PAO synthetic anymore. Last visit to Walmart and they had none on the shelf. Unless you are going to run a high end synthetic like Amsoil or Royal Purple, you most likely will be buying a dino Gp III synthetic anyway. Almost all of the "synthetic" motor oils are like this as the Eythelene gas to make PAOs has become hard to get and expensive. If you are an Amsoil/ Royal Purple user, I would suggest buying up a bunch as these manufacturers don't have any choice about either reformulating to a Gp III or going up considerably on the price. And if the seals do start leaking all you have to do is buy a bottle of Auto RX and run a dose thru the engine. It is a lanolin ester that conditions seals and also works as a slow flush. I don't recommend a "quicky" type flush as they drastically reduce the viscosity and literally strip an engine. Sometimes causing more harm than good. FWIW, no synthetic will make your engine last one mile farther than a quality dino blend. The advantage of the synthetics is extreme cold start up issues. Other than that, they don't produce any lower wear metals and if you have an overheating situation, the oils meeting Fords Specs 929 and 930 will stay with you until the engine is toast anyway. Your money- your truck.