I'm in the middle of a rebuild right now and my mechanic says I may want to consider no longer using synthetic. I will be using .0025 bearing clearances, hardened Federal Mogul bearings, about 500 rwhp and 6,300 rpm. He says in his experience the engines that he has torn down that had used synthetic oil always look worse than engines that used regular oil. He says it's just too thin for his taste and doesn't seem to offer enough protection, he also says a local race engine builder says to never use it in a race engine. What gives? I always thought Mobil 1 5w/30 and 10w/30 were the way to go period, no?

 

maybe its because some people use synthetic for around 10000 miles.

 

My recommendation is this. Stick with the synthetic oil. For me I have been using the stuff in my cars and have had no problems at all. When I torn down my LT1 after 114,000 miles(95,000+ were supercharged), the motor was clean, and was still within factory new specs. This is even in the #1&#7 where I cracked those ringlands. I compared my motot right next to another 350 that was in my buds shop and it was night and day, next to the other motor that used regular oil. I was still able to see the factor cross hatches in the bores(my motor). I think your engine builder is old school and just whats to stick to what he knows. In any case that's my 2 cents. Good Luck

 

197,000 miles and since the first oil change it has had nothing in it except Mobil 1. Had the valve covers and intake off once for a intake leak. Inside the engine was real clean for 140k at time.

 

Just use the regular stuff for the first few thousand miles to seat the bearings and all. After that, run synthetic.

 

In the morning, I'm going to reply to a post from a few weeks ago with details. But, basically, there is a salesman comes into a local tranny shop where a buddy of mine works. He has a 96 Toyota or something (4 cyl) and uses Mobil 1 15W50 and has since the car was new. Car now has 632,000 miles on it and the valve covers have never been off this engine! I'll post details about it in the other thread but I think 632,000 miles without a rebuild is fairly impressive. I would think the synthetic oil played at least a little role in that

 

Several transmissions and a few driver's seats later...

Does that guy literally live in his car or what?

 

Maybe he just meant for the break in period? that would be the only time you don't want to use synthetic.

 

Actually, I think but am not sure that he has only ever had the transmission SERVICED... not even rebuilt but will find out tomorrow. The car is in pretty decent shape considering. He is a traveling (duh) salesman who does more traveling than selling I think He changes the oil every 3500 to 4000 miles. I've got pics and details but don't have them with me. I got the info for the 15W50 debate that was going in the other thread. I'm no oil expert but it seems the engine builders at elast down here (in sunny Florida) favor 15W50 even in new engines and since there often times is talk about 15W50 being too thick, I just wanted to post some info about this 632,000 miles car to show that it might not be all that bad... at least down here

 

What we really need is something to make the AC colder in the summer time.

 

It's generally a bad idea to use synthetic for the first 7,500- 10,000 miles, because you don't want to interfere with the normal break-in process of the bearings or rings.

After that though, use synthetic.

And if you are running very tight clearences, DON'T use 20w-50 or 15w-50.

I personally use 0w-30 in my station wagon, which is a 2000 model, and 10w-30 in my LT1, which has over 130,000 miles on it.

 

My father in law had a 96 or 97 toyota tacoma 2wd with the 2.4l I4 that he bought new and drove for his small courier business for three years. He would drive packages from the philly area up and down I95 to NYC & DC every day for three years. He put 430,000 miles on this truck during that time before he sold it and the only major repair was the auto trans was rebuilt at 250,000. The motor was untouched inside, nothing done but routine maintenance and it was still running fine. He changed the oil himself religiously at 3k miles but he used the cheapest stuff he could get, that $.99 cent/qt junk.

This truck saw all hwy miles it's whole life and didn't have enough power to get out of it's own way but those little toyota 4's are one heck of a reliable little motor if properly maintained. Of course it probably would have seen that many miles on synthetic too, just want to mention that even on 'cheapo' oil those motors can still go on for ever. Not trying to say synthetic isnt necessary, I run Mobil 1 in my Z but I like to run it very hard, but I don't put synthetic in my other vehicles. I just think synthetic is much more important in motors that see a lot of hard driving, I don't think it's that necessary for the average 4 banger that never sees any abuse in it's life. Just my $.02.

 

Who are you having build your motor? I haven't looked hard but I also haven't heard of anyone in this area to do the work. Just curious for the future.

 

Maybe we should trade in our f-bodys and buy toyota's.

 

My engine builder told me to us 20-50. He didn't care if it was synthetic or not (after the breakin period). If you don't trust your engine builder to accurately specify your oil you should be working with someone else.