I'm doing my rebuild in a few weeks. I want the longest life and best performance possible. What kind of oil do you guys use?

 

Valvoline 10w30. i change it about every 2500 miles. if it was a new motor i'd probably go with Mobil 1 synthetic which everyone says is one of the best.

by the way, orlando here also.

 

run regular oil during break in and then switch over to synthetic.

 

i used to have a little knock on my driverside valve cover nut after synthetics it went away now runs great

 

Mobil 1 here.

Amsoil is also atop the list, just harder to find in stores.

 

Yup

 

I just switched to synthetic in my 140K 305. So far for the last maybe 400 miles it hasn't started leaking that I've noticed. I'm gonna keep an eye on it though. It still smokes for the first 3 seconds I start it up, cause the valve seals leak a bit but it doesn't seem worse than before.

 

I was running synthetic only on my motor. Ive concluded it wasn't breaking in with synthetic. 4000 miles and it still burns alittle oil and the oil gets nasty quick. Im gonna switch to regular castrol GTX for a few changes and see if it stops. If it does im switching back to mobile 1 synthetic.

 

you have to run regular oil for a while when you first break it in or the ring won't seat... that may be whats causing yours to smoke

 

synthetic here when I have the money
and after I get my turbo motor in all the time
prolly going to run castrol syntech


what are you guys opinion on castrol sytec vs mobil 1?

 

Valvoline 10w30... I tried mobile 1 synthetic for a couple of oil changes just to see if my fuel mileage would increase, mileage stayed the same so i changed back.

 

Another vote for Valvoline 10w30... with 248,000 miles on my original motor, I'm not moving to synthetic! I'd have so many leaks, it'd be like a watering can.

 

I'm running castrol 5w30 for the first 3500 miles. I was going to switch to castrol syntech after that. What do you guys think?

BTW- I change my oil very often. It is not a daily driver. I might put 2500-3000 miles on it this year. The motor went in last march and I have just over 2200 miles on it. I changed the oil 8 times.

 

Valvoline 10w30 here too every 3K miles. (Abt 95% is highway miles.)
IMHO, syn is only needed where oil temps stay really high, like with a turbo.