This past week I decided to switch the rear end and trans gear oil from conventional to the synthetic Royal Purple. After driving the car, I have noticed a smoother and quieter drivetrain. I havent used it in the motor yet, as she is using oil due to valve seals and guides.

Has anyone here used synthetic in their engine and if so , what difference if any did you notice?

 

I have around 6,000 miles on my 331 and im now using mobil 1 and it runs much smoother.I like it much better.It even lowered the temps by about 10 degrees as well.

I just changed my rear ends oil also but im using castrol synthetic and i like it as well very nice gear lube.

But i spilled a few drops of friction modifier on the garage floor and OMFG that **** stinks!lol

 

Having run synthrtic oil in everything I own, I can say it is great stuff. The biggest difference between oils is synthrtic oil will not breakdown like conventional oil. You can easly run for 7500 miles between oil changes. I have a 97 cavalier with 172,000 mile on it and I chance it every 10,000 miles. (all freeway miles). The important think to remember about synthrtic is you have to wait to change over after the piston rings seat in a new or newly overhauled engine, around 10 to 15 thousand miles. Better performance is noticed at the gas pump and no repair bills on my motors.

Vince[sm=smiley20.gif]

 

i am a gm asep student at guilford tech but i own a 67 pony we just completed last semester a course on oil viscosity and ect. by far and away synthetic is the way to go don't use it to build an engine but after initial ring seat it is ok to switch. at the dealership where i work there is a huge difference in the engines we tear apart on the ones that run synthetic vs conventional. the synthetic engines are like new inside.

 

Thank you for the replies, good information!

 

I have read two different things in these forums:

1) Synthetic Oil SHOULD be used on '65-'73 Mustangs
2) Synthetic Oil SHOULD NOT be used on '65-'73 Mustangs

Which is true?
Are the seals really that much different? It will cause leaks?

I'm confused, I'm hoping I'm doing the right thing by running synthetic right now. Does anyone know for sure?

Thanks

Greg

'65 Fastback
289 4v Holley

 

the difference is the gasket material...engine built in those years the gaskets weren't a very good quality gasket and in the late 70's syth oils started to appear and leaks started in these engine...with today gasket material and adhesives leaks are less likely in and older engine....if you car leaks or smoke DO NOT USE SYTH. OIL

 

i agree, dont waste money on syn oil if your car burns it, but synthetic oil wont leak any more than an organic oil....back when sythetic was fairly new, it did leak alot, but todays syn oils have additives to prevent leaks

 

David, I was just wondering what types of failures you are seeing in engines run on synthetic.