in 1956 bought new 56 porsche speedster the first syn, oil was Steinoil was clear and smelled like nitro have used only syn. every since why take a chance cost is very little when compared to the benefit. should read Stein C made in Salt Lake, Utah.

 

By using synthetic oil on 2.4 auto, is there an increase in mpg, engine smoothness, performance?

 

What about an engine that has been getting syn oil for 150,000 miles and switching to dino oil?

Good/bad/indifferent?

 

i wouldn't. but i do not think it would hurt anything.

but going the other way, putting synthetic into a high mile engine that has only had dino in it, could cause seal failure and oil might get by the piston rings.

 

That won't hurt anything.. Happens more that one might think.. No Biggie..
& I build motors...

PS: But agree I would not go to Syn @ 150K from dino..

 

Valvoline SynPower 5w-30 In the Deer Slayer.

One point to remember is your oil needs to be cleaned, so I change my filter every 3000 - 3500 miles. The easy access and the fact that you can change your filter with very minimum oil loss helps.

 

The "seal failure" that some have experienced in switching to synthetic oil comes from synthetic oil's cleaning properties, which clean off varnish deposits. Many times these varnish deposits are the only thing keeping an old seal from leaking, acting as a labyrinth seal. The seal was well on it's way to failure.

 

Thanks, we're selling my wife's Benz, and the potential buyer is a bit put off by $60 oil changes.

 

Is that price @ Benz dealer, that sounds too low.. Them & BMW like to make your trip worthwhile for them...

 

Generally the molecules in s syn oil are smaller and may leak on older engines. Front seal on Chevy Rear main on Pontiac etc.

Most older engines had leak prone places to start but the smaller molecules help it leak a little more in some cases.

It is usually not enough to hurt anything but can happen.

Most modern engines today are better sealed and this is no longer an issue on most new cars.