Alrgiht its time for me to change the oil in my car and dont know if it is worth changing over to the synthetic stuff any help would be appreciated. THanks, Dan

 

Synthetic has lower friction and is way more tolerant to high engine temps. After 65000 miles of Mobil One, my engine internals were like new.

 

Synthetic oils flow freer during cold weather and cold starts
Synthetic oils take longer to break down
Synthetic oils adhere to engine parts better

 

synthetic oil may also cause oil leaks if you have many miles on your car.

 

i got abpit 90k on the clock, how does it cuase leaks though and would i be at any risk,

 

if you dont have any leaks now you should be ok, syn oil is alot thinner than dino oil

 

I don't think synthetic oil causes leaks, I think it's better at finding places where you were going to eventually have a leak. (Which may be what you were actually referring to.)

 

That's a bit of myth. Synthetic oil is finer than a dyno oil. If there is a pre-existing oil leak more synthetic oil will leak out than dyno oil. Checkout http://www.bobistheoilguy.com/ for some great info on various types of oil.

 

I've used synthetic (Mobil 1) since I've owned my car (~50,000 miles) and now with 145,000 it doesn't burn a drop of oil between changes (every 5000 miles). That pretty much speaks for itself.

 

Not true, not true, not true!

Lower weight oil flows freer in the cold. Syn. have the same weight.
Syn. oils do not CAUSE oil leaks.
Syn. are not thinner. They have the same weights. A 30W, is a 30W, is a 30W.

 

Synthetic is the "real stuff".

Synthetic does not "cause" any oil leaks. The leaks are already there.

 

It is definitely true, synthetics flow much better in the cold. Just look at the pour points of Mobil 1 5w30 compared to conventional 5w30. Or how about the 0w30 Castrol SLX from Europe, it's got a pour point of -80F! You'll never see that with any conventional oil.

 

i was told that synthetic oils may help clean the engine out which may cause you some leaks around seals and such.

 

maybe true... but like some guy already said... its really just finding and addressing already-present problems...

thats kind of like saying.... "honey, the kitchen is on fire".... "well close the door".... your going to find out you have a problem and need to address it sooner or later anyway... i would rather change seals, then NOT have leaks or blow-by because of build-up... and synth. is much better for your engine

and yes IT DOES flow better when cold...

the weight has nothing to do with it... its about molecular size...

rough example:
you could have 1 quart of dino oil with 100 square milimeter molecules...
and you could have 1 quart of synth. oil with 1000 molecules of a smaller size...

same weight... easier flow...

forgive my crudeness...

 

It is worth remembering that the viscosity ratings are at set temperatures. 5W-30 demonstrates a viscosity of 5 at -18 F. and a viscosity of 30 at 212 F. Dino or synthetic, a 5W-30 has those characteristics at those temperatures.
Move to a lower temperature, like say -50 F. and the synthetic will still flow, while the dino oil will be a semi-solid, like frozen yoghurt.
Move to a higher temperture, like say 400 F. and the dino oil will be blackening and thickening, and the synthetic will be just fine.
So within the API test range for multi-grades, both will measure similarly, but outside those tempertures the oils will be very different.
I have heard "about" synthetics leaking more. I have never seen it happen in over twenty three years of using Mobil 1. In fact I am quite tired of hearing "about" things from people who have never seen them. The same is true about the myth that synthetics "clean out all the deposts that are important to clearances and sealing". What a load of crap. Deposits are bad period.