I've always heard that you shouldn't use synthetic oil in an engine with over 75k miles unless it's been run with synthetic it's entire life. Is this true? Somone told me the other day that they switched over to synthetic at around 100k and have had no problems... my Integra has 74k miles and I've always used synthetic blend because its much cheaper, but now that I'm doing my own oil changes I could use a full synthetic and still save money...

BTW how often do you guys change your oil? I've always changed mine every 3k, though this time its probably been at least 5k since the last change (oops)... I'm sure every 3k is excessive, but it seems like cheap insurance and the car definately runs better with new oil in it...

 

I've never heard anything like that... I got my car with 60k and started using fully synthetic right away. Don't know what the old owner used. I would recommend a full synthetic oil though... runs pretty good. I use Mobil1 Tri-Synthetic 10W30 (not sure what makes it Tri-Synthetic).

Going 5k would not hurt the engine. 3k is a conservative number... service recommendations have a big buffer zone, so you have nothing to worry about. I change mine every 3k just because I drive hard and to be consistent. My mom has gone 10k in her van (which really ticked of my dad), but no damge to the car.

 

I also got my car at 60k and started running mobil 1 synthetic. But for some reason it seems like I have heard something to that extent before just cant remeber the specifics.

 

I got my car with 103k miles on it, and i've been running amsoil fully synthetic oil ever since in my engine and tranny. i love it. the synthetic might slowly "leak" out if you have bad or deteriorating seals and gaskets, but if they are going bad they need to be replaced anyway. i had a tiny bit of smoke for the first day or two... but that went away real quick.

 

Unless you are running very hot you really don't need synthetic. Just make sure you are within the proper temperature/viscousity ranges. I just tore down my block and the mains were all smooth (except 1 and 5 which showed typical wear patterns). My neighbor who does domestics thought mains 2,3,4 were new. The engine had over 134K.

 

I put in Mobil 1 synth at around 90K miles and have used it ever since. The oil pressure sending thing developed a leak but other than that has worked great. I've had people watch my tailpipe for smoke when at full throttle/ high rpm's; they saw nothing!!