Is it a bad idea to switch from conventional to synthetic oil after 100k miles? I know synthetic is better, but is it really worth using it at this point? Otherwise, what do y'all think is the best conventional oil?

Synthetic may bring out leaks that wouldn't normally show with conventional Dino oil, because Synthetic is Thinner, or some thing like that.

Synthetic may bring out leaks that wouldn't normally show with conventional Dino oil, because Synthetic is Thinner, or some thing like that.
honestly i would not switch now,unless you replace all your seals before,it may not leak,but what happens is synthetic oil is VERY "cleaning" and it may remove some "junk" near your gaskets/seals which will start a leak,i had a t-bird that i put synthetic in for the first time at 120k it never leak a drop till then,it started leaking within 100 miles ,i mean it dripped slow and steady,i pulled the syn out thinknig it was too thin,but it was too late the junk was out and the oil could now leak by the seals,it was years before i read a report explaining it wasnt to thin,it was too cleaning!!!

it will help your engine last longer, but might leak,, :(


mike

Same thing happened to my Suprcoupe the first time I got her, and before replacing the motor.

On the original motor, it started leaking through the valve covers. I know, the 3.8 valve covers of the time were prone to leaking, but the Synthetic made them spring leaks within one oil change.

i swapped to synth at 83k on my old motor, and it never leaked any oil. when i tore that motor down, it looked awesomely clean..

I switched to Mobil 1 @ 97k miles. Only been about 1500 miles so far no leaks. Sure hope not !!!

my guess is that you will develope the leak in the first oil change,if not,your probably good to go with synthetic.


mike

Just switched to Mobil 1 Synth at 86K myself, so far I've only gone about 200 miles so it's too early to tell what's going on. It definitely runs a little smoother, but because it's thin stuff my timing chain guides make a little more noise on startup than they did before.

Steve

The same thing happened to my buddy's Mustang, he switched to synthetic and voila!!!!! Leaks galore!!! It wasn't even a high mileage car, I think it had 60,000-70,000 on a '95. After it leaked, he tried Lucas oil stabilizer(which i hate) and it seemed to leak less.

ya I have 97k miles on the car right now, I won't even bother with synthetic, not worth it. With my luck on cars, it's gauranteed to leak, I'll stick with Valvoline or Quaker State 5w-30.

I switched to Mobil 1 at 110k miles and no leaks.