Striker223

On the hundreds of cars I've worked on I've never ever seen an issue when switching that wasn't already there. Most people do not really inspect an engine for leaks and with conventional oils inferior flow and molecule size it may only wet an area and not drip. The leak is still there however and synth will never cause a leak.

My friend just got a 09 ES with 158k on it, second day he owned it it was switched to full synth mobile 1, no leaks will appear since he car didn't have any before the switch. It's a superior oil to any conventional and unlike what the selling dealer put in the car the correct weight too lol!

I switched my 205k mile LS engine to synth when I got it as well, zero leaks were caused. I also switched my 220k mile Jeep when I replaced the one seal that was leaking and now at 290k it doesn't leak at all. Same story with dozens and dozens of cars, if there is no leak there is no leak. It's not the oils fault you are unable to identify it beforehand, it will just make it very clear you missed something during your inspection.

Conventional oil will kill your seals faster btw, it will breakdown more easily and build up more acid under the same conditions than a synth. If you really care about stopping leaks and preventing main seals from failing you will not use it.....to say nothing of the myriad of other benefits.

tolian21

Scotty advice is good for me, also heard it from other mechanics and information on internet. Synthetic washes stuff better, so any deposits will be washed away. Its your car, do what you wish.

tolian21

synthetic oil is much better at cleaning sludge in the engine than conventional oil. If he has bunch of sludge there and seals are barely holding up, it will clean it well.....

Wilson2000

I'm a fan of Scotty, but our opinions differ here. Too, I don't buy your "washing" argument as both synthetic and conventional use the same detergents.

What I may buy into is this...Conventional oil breaks down under heat and load and the byproducts of this, sludge, may mask leaks. However, the byproducts cause all kinds of other issues as well, and an oil that has degraded will not lubricate the entire engine as well. Pick your poison...an added risk of leaks, or, a premature engine failure. I know which one I would choose!

Wilson2000

Check out these videos for further info on this topic:

tolian21

So if I have 15-20 year old car with 300K miles thats been using conventional oil and has no issues, I need to change it to synthetic oil? You folks do what you want with your cars. I've been running mobil1 EP or pennzoil in all my cars that I bought new, but I would not recommend anyone taking their high mile 20yr old beater that still works great and say "you better switch to synthetic NOW". No mechanic will advise that, but sure there are all kinds of documentation from Amsoil and Mobil1 of how you should make the switch, and how leaks are not caused by synthetic oil and etc, I've read them all.

Here is Eric car guy https://www.ericthecarguy.com/forums...synthetic-oil/. He mentions, you get an old car, you put synethic and you notice a leak. He does say that its not a synthetic fault, with which I agree. But who cares?? it was not leaking, but now its leaking and you need to pay $$$

Wilson2000

Who said that? I only shared my experience and research. I didn't make any recommendations. To each their own. Live and let live. Etc, etc.

Striker223

No you don't. You can be lazy and just switch back to conventional and make the leak "stop" it was already leaking after all.

It also depends what you want out of the car, I switched my 430 to synth because I redline the hell out of it and it sees 120+ very often and that demands a lot of very high sustained revs and oil abuse that I don't want to leave to chance with lesser products that cost effectively the same as superior ones.