Switch to Full Synthetic Oil

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Shane

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I started my rebuilt 340 and changed the oil on regular break in schedule 10w 30....I now have put about 1100 miles on the motor and was thinking come spring I would change it out and fill her up with 5w 30 Castrol full synthetic..

Does anyone see any issues with this?

Is it worth doing this?

Any better full synthetic I should be using?
 
I`ve always heard that the old school seals would`nt hold up, and leak. But I`ve recently tried it, and seem`s to be holding up so far. I`ve also felt a slight increase in power. I`m a valvoline man personally. Mobil 1 is also a good product. They`re all probabley good these days. I change my oil every 3000 miles anyhow and shy`d from the expense of synthetics, but decided to splurge. ha
 
This might be a touchy subject, but if you are going to get modern synthetic oil then you should put in a flat-tappet cam additive so you don't wipe the cam (unless you have roller lifters) or just go with an oil that has sufficient levels of ZDDP. Besides that go ahead, I switched to synthetic in my 318 just to be nice to it.
 
I do it all the time with my race engines. I break them in with conventional oil then switch to 5w-30 or 5w-20 Amsoil synthetic. I did it with my 2004 diesel, going from conventional 15w-40 Rotella to HD 15w-40 Amsoil and currently have Series 3000 5w-30 Amsoil in it. I will do the same in my 2005 Dakota which had an oil change when I bought it last summer. Synthetic Amsoil going into it also. Never had a problem. (I've had some minor rear seal issues over the years with both conventional and synthetics.)

There are several Amsoil synthetics that still have high concentrations of zinc, including some of their their diesel and Dominator race oils. There are some others but I can't find the info at the moment.

When there are leaks after a change, it's usually from old gaskets that have started to lose plyability and may have had gunk accumulations over time which got cleaned out by the new synthetics. Synthetics can find marginal seals and leak a bit easier.

Amsoil source and info: www.thelubepage.com
 
I kinda figure our fathers and our fathers' fathers used conventional oil... and did just fine... is it worth the money? But then again... Royal Purple "proves" that you'll have HP gain... ...
 
thanks for the replies...Maybe I should just buy a good semi synthetic and be happy in the middle ground...ahahaha

I have the whole winter to let this one bounce around in my head...
 
I think no matter what you decide to use, you should change it before you store it .. I've always liked the idea of fresh oil in the engine when it's gonna sit for a while.. That way you don't have all those contaminants clinging to the walls of your cylinders, corroding them.. I also had a very reliable engine builder tell me to rev the car right before storing, and pour in some Marvel Mystery oil until it stalls, to coat the cylinders and prevent a ring from sticking.. Makes a mess in the spring, and spark plug changes are inevitable, but the theory sounds good..

I agree w/ Locomotion too about the older seals, etc.. Back in the day I had a '71 Chrysler 300 w/ a 440 in it .. I switched to Mobil 1 synthetic when it first came out and suddenly I was adding 2 quarts of oil every week.. I think with your "fresh" engine that won't be an issue ...
 
I wouldnt worry about changing to synthetic. But I would use something heavier in grade like 10w40 or so.
 
Thanks 66dart...that was the second worry in the back of my mind...

I am not sure of what the different oil weights do in the motor.

but i will use the 10w40 if i do go with the synthetic...
 
Thinner oil circulate faster, especially in cold climates and on start-up. They can also provide a slight mileage and HP increase. But it's not enough to worry about in a street or dual-purpose vehicle.

You can also use thinner oils if the engine was assembled with clearances on the tighter side.

I read somewhere that wider viscosity spreads weren't always better. But I forgot the details. 10w-30 would not be bad. Some people run 15w-40 diesel oil. But the most important thing is to get a GOOD quality synthetic. There is a variety, including within brands. Even there, some have more and some have less zinc. Do your homework. Personally I prefer Amsoil.

www.thelubepage.com
 
When I'm done with my '68 I'll break it in with conventional then switch to full synthetic. I'll be running Royal Purple 5 or 10w30. My build will include fairly close clearances.
 
I have run Mobil1 15W50 in my 340 since after the first oil change at 3000 mi. I also use the Hughes oil additive since I run a flat tappet cam. When I put the Edelbrock heads on, I couldn't believe how clean the engine was. I'm sold on synthetic. When I used conventional oil the inside of my engine wasn't as clean.

Fred B
 
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