Just my opinion here: NEVER put synthetic in an old motor that has used petrolum oil its whole life! Nothing but problems there! Some folks have had good luck there,but i STILL DON'T RECOMMENEND IT! Use your own Judgment-because oil leaks will follow! Have fun spending the extra you dont need! Myself,I'd put it in my gas tank! Best of luck to you my friend!

 

There can be some oil leaks in older engines NOT because synthetic is "synthetic". It is because synthetic oil is USUALLY very much thinner than conventional oil.

Put some 5w20 conventional oil in an older engine it it will leak just as much as if it was synthetic. Put in 20w50 if the older engine leaks oil.

 

Word to you all! Don't EVER put synthtic in an old GM motor! (1987+)Unless you have totally rebuilt it! Case in point! Bought a new 1984 3500,changed to syn at 30K. developed major oil leaks!But in a shop built 68 350 for my 66 truck I used syn after break in and never had a stitch of problems! Gasket issues? I think so...Do your homework!

 

Ive never noticed any increase in leakage from synthetic. Been running it for many many years. Honda, GM, Nissan, Ford, briggs and stratton ect

 

okay running a engine with no thermostat will not make it overheat but not letting engine get hot enough will cause condensation and will cause it too magically have milky looking oil becouse its not heating up enough, sounds crazy but true.. also can make engine think its still cold and burn more gas almost like a choke mode. Anyways engine acts as if its sweating if not up to operating temp and wont burn it off so sludge effect happens

 

i know that synthetic is great for newer engines but its a very high detergent and can cause any sludge that is built up on oil control rings and even the cylinder walls and cause it too wash it off too the point of loseing some compression and if u do got any leaks it will clean any deposits thats keeping it in a way plugged up from leaking lol.. If u do anything with the oil id just stick with regular oil like castrol or whoever u like but Id steer away from using synthetic honestly if its getting higher in miles or has any kind of leaks