I took my my moms van up to the quik lube the other morning and told the guy to put in the 'high milage' motor oil since its got 109,xxx on it. He asked me if the vehicle had run partially/fully synthetic motor oil in it. I said yes that we had run the high milage oil since around 75,xxx. So he put it in but he said something about if the vehicle had high miles and had always run a certain type of oil that you shouldnt change it. He said that putting full synthetic motor oil in the van would be 'risky' and that he would not do it if it was his car.

How would synthetic oil potentially hurt a motor thats got high miles and never run syn?

 

I read on a oil forum long tme ago that synthetic oil has particles of the exact same size, and very small.
Regular oil has particles of different sizes. The guy was saying synthetic is more likely to leak in vehicles with higher mileage.
Not sure if this is the answer u want, but i just remember reading it.

 

I put Amsoil in my 1990 Honda 18 months ago for the first time. It had 120K on it. It runs like a dream. An excellent, no frills, point A to point B automobile.

I wouldn't worry about it.

Hunt4Fun

 

Green_98,

An engine with 109,xxx miles that has run "dino" oil will have more "sludge/varnish/crud" than an engine that has been running "synth". This "sludge/varnish/crud" may be the only thing preventing leaks through dry gaskets/seals etc.

Since "synth" oil is a better solvent than the "dino" it will dissolve the "crud" and allow leaks through those old gaskets.

In short, the reason you shouldn't change to "synth" is the same reason you wouldn't use a strong engine flush on an "old" engine.

That's the theory and it doesn't happen in every case. But it is a chance you take.

Good Luck,

Bill

 

cool---i learned something today

 

I agree with what wmcnally said..... That's basically what the Mobil 1 site says in it's FAQ section too...... I put M1 in my wifes 120k mile Plymouth Acclaim because it's driven daily, but for only about 15 miles total!! It does not leak a drop. It gets parked in the garage too, so I'd know if it was dripping!

I know this is the worst kind of miles to be putting on an engine, but the M1 should help keep it from "sludging" up compared to running it with the dino stuff....... We try to take it out for a nice highway run once a month too.......

Just makes me feel better about the whole thing. Whether it does any good or not, who knows.......... I also put it in my F150 at around 80k miles and it's got 111k on it now, but I also put about 50 miles a day on it with 40 of that on the freeway!

I also don't believe in that "high mileage oil" that says you need to start using it at 75k miles.............. I still use 5w30 in the Acclaim and my F150 and there is no hint of blue smoke coming from either of them. I'll bet if you have a motor that's smoking now, it'll still smoke even after using that "high mileage oil", JMO however....

 

Red Line! or Mobil 1

 

Patrick,

you can change to synthetic at any miles, and back to dino again no problem. The only problem is gaskets leak when they get old reguardless of the oil you use. If you have a leak now with dino oil the synthetic will leak out at a faster rate. If you don't have a leak, then it's not an issue. Some times the leak is so small that you don't notice it until you put in synthetic.

A leaking gasket is also an indication of sludge since the oil flow is designed to lubricate engine parts, not gaskets. Treating your engine with Auto-RX then changing to synthetics will reduce or eliminate leak problems.

'Risky' is a strong word, probably means he has seen problems he does not understand. This is a quik lube right.

If you change to synthetic and notice a leak you can change back to dino. I've done it. OTOH, if the engine has soo much sludge and the gaskets are soo bad that the sluge is holding the oil in the engine, then maybe this engine is not worth the expensive synthetic oil.

 

Dont listen to what the 'Expert' at any of the quickie oil change places tell you! If you have to use the quickie type places, it would be a good idea to stand there and watch everything they do.

 

I agree with that 110% and also like to add a strong emphysis on WATCH EVERYTHING.