Regular Or Synthetic - Which Oil Should I Use?

[Renderhaus]

Just purchased a '93 with 88k on it. I'm not certain, and have no way of knowing whether or not synthetic oil has been used in it up until know, but I'd like to start using it from here on out. However, I've heard that it isn't good to switch from regular to synthetic after an engine has reached a certain mileage. Something about it doing more harm than good. Can anyone shed some light on this? Would it be benificial for me to switch at this point?

Thanks.

[JDOwen2]

When I bought my 95 it had 90,000 miles. I started using Mobil 1. A few weeks ago when it turned 103,000 I switched to Amsoil. You shouldn't use synthetic oil to break in an engine. After about 10,000 it's ok to use synthetic or even switch back and forth between the dino and the synthetic.

[SAMOHT023]

I use Amsoil 5w-30 synthetic in my 93 sc400. I use Amsoil synthetic differential fluid as well. The only major difference I notice is a slightly lower temperature hand than when I was using conventional oil. I dont think it makes much difference as long as you change the oil regularly. The only advantage may be that you can go longer in between oil changes with synthetic versus conventional oil. I change my oil every 5000 miles and my rear differential fluid every 50000 just to be on the safe side. My SC has 175,000 to date with no major mechanical repairs required. Knock on wood :D

[jcm3]

Planet soarer has documented that regular dino oil is best and doesn't offer any performance or longevity increases as long as it is changed regularly (3000) miles. With synthetic the oil changed can probably be extended to 4-5000 especially when using royal purple, amsoil or redline.