Which oil??

[Lifeson1]

I bought an 84 SWB with a recently rebuilt 350... less than 1000 miles on it. No oversized cam I know of of...About to change the oil ( already drained)...I have plenty of oil in the garage...choice of 10/40, 10/30 and a syn blend of 5/30... Would a 10/4- be too thick? The oils I have are all off brands made by Martin, one called "Unigard" and the other branded "Xtreme" my wife picked on clearance..Only the 5 and 10-30 have API certified certificate tags on the bottle..... dont wanna jack anything up. Prompt response appreciated...truck is sitting under my giant sycamore tree (98 degrees F in the shade)awaiting......thanks.

 

[1low4x4]

do the 5 30

 

[DoubleDingo]

I use Rotella T 15w40 with some rislone zddp additive. These flat tappet engines need a zinc additive. I never knew this until about a year or two ago.

 

[Lifeson1]

I went with the 5/30...I do have some rotella...15/40..thought about that. Thank you.

 

[skysurfer]

Late post since your already done but many guys won't run synthetic or a syn-blend until they are sure the engine is fully broke in. At 1000 miles, maybe yours is and maybe it isn't. Either way, I would still change the oil again in 3k. I'm with DD on Rotella, it's about as good as you can get. Not sure if the extra Rislone additive is necessary since Rotella is rated for diesel use and already has extra zddp in it. Couldn't hurt anything to add some in, I knew an automotive engineer years ago and he said Rislone is a quality brand.

 

[77 K20]

I use Rotella T 15w40 with some rislone zddp additive. These flat tappet engines need a zinc additive. I never knew this until about a year or two ago.

I agree on researching zinc for oils. Found out the hard way when I ran cheap oil in my old 400 and had some lobes on the cam get ground down flat.

 

[MikeB]

I agree on researching zinc for oils. Found out the hard way when I ran cheap oil in my old 400 and had some lobes on the cam get ground down flat.

Yeah, it's no fun at all, especially in a fairly new engine that you just spent lots of time and money on. Had a customer go through that with a 454.

For flat tappet cams, break-in is VERY important. I like to use Joe Gibbs Driven BR30. After 400 miles, I use something like their Street Performance oil with proper levels of zinc and phosphorus. However, If the valve springs are stock or mild (70-90# closed and 250-270# open) you should be OK with Valvoline VR1 in the silver jar. Or even Mobil 1 10w-30 has more ZDDP than most oils at the auto parts store. And it cost around $25 for a 5 qt jug at Wal-Mart.

Not being a chemist, I stay away from additives. If you just gotta use ZDDP Plus, or a Lucas additive, or whatever, please make sure you know your oil's ZDDP levels before simply dumping in a bottle of additive. An oil with the proper levels and balance of zinc and phosphorous BLENDED IN is a good thing, but don't assume adding a jar of additive to the regular oil will accomplish the same thing. It's the ENTIRE designed-in additive package that's important.

 

[Camatruder]

Every how many miles do you guys change the oil when using synth 5w30 with only street use in moderate climate?

 

[skysurfer]

Most manufacturers recommend 7,500-10,000 miles between oil changes when running full synthetic. Mobil 1 Extended guarantees their oil will protect an engine for 15,000. My dd ('04 Honda) gets changed at 6k because I drive it like a madman. The square gets traditional non-synthetic because it gets used offroad and I can't break the 3k mile habit with it. One thing to consider with the 7-10k mile recommendation is that the manufacturers are referring to cars made with improved engine components and much tighter tolerances than squarebodys ever were. I wouldn't consider running the 5w-30 that the Honda gets in the Suburban, and I think the Honda would choke on the 15w-40 that the Suburban gets.

 

[77 K20]

I use mobile 1 synthetic and change it every 5,000. But I use the truck in dirty environments and often are climbing mountains.

 

[Jim Hensley]

the lower the first number the faster it gets to where it needs to be when its cold. Just remember that,