Hey guys, well previous owner ran 20/50 QS oil in this motor for years. I am thinking of changing it in the near future. I know that the clearances in these old big blocks allow for a heavier oil but is 20/50 to thick? It came from a hotter climate compared to where I drive it now (Victoria). I idle at around 20-30psi and get as high as 65psi when accelerating. I am curious as to what other guys run in their big blocks. I am hoping to use the same type of oil to keep the motor happy but if a change is recommended than I'll have to explore other options for what oil to use.
__________________
"no one ever called the fire department for doing something smart"
I did some research and what I came up with is / older big blocks used old iron and the new oils do not have any zinc. The most zinc in any oil is Rotella by Shell and it's a diesel oil...roughly 20/50. This will save your Cam Shaft...new oils have no zinc and will cause metal break down. I have personally switched to this oil with the research that I have done. I have been able to purchase it through Lordco...it is not expensive.
I run 5W40 synthetic diesel oil in all my engines. You can add GM EOS suppliment if you are worried about the zinc. Most Diesel oils have the zinc if they are the pre-emissions design. Some of those products will be available long term it appears. The thoughts here are if 90% of engine wear is within the first 2 minutes of startup then start thinking about the thick cold oil and what damage it is doing during warmup. Most people don't realize how long it actually takes the oil to warm up either. This train of thinking says, go for the high tech oils that are thin when cold and thick 40W film strength when the temperatures are high. This really gives you the best of both worlds. The newer engines go with 5w30 or 5W 20 synthetics. The new stuff has tighter bearing clearances and therefore only go with 5W20 or you will be doing the bearings. 20W 50 is really heavy cold and is a 50W when hot. ( the first number is the cold spec, the second number is the hot spec) No not even big blocks are designed to run there. Does is work, you bet especially if you are racing and that engine is running at extreme temps all the time and you are dumping the oil a lot and you are doing teardowns and extended wear is not an issue anyways. I used to use it when I was running my smallblocks to 7 grand too.
... my 2 bits
-- Edited by Elroy on Wednesday 1st of September 2010 09:22:31 PM
In the research that I did I found that synthetic is a bad word for older engines. In a brand new engine they are fine, but in a older style engine it is harmful. The engine will leak and burn oil after awhile because of older style gaskets and piston rings. From that I personally will never use synthetic oil in my 67 beaumont 396 EVER!. Just my opinion take it or leave it hay its your car.
There have been some instances years ago when there were chemical synthetics on the market and some engines went south. Some of those products ate out the seals etc etc. Nowadays though the mineral synthetics will totally mix with regular oils, they don't wreck your engine. The only reason you might get a leak or some blow by is because you are running on lighter oil for the complete warmup period and if the engine isnt tight, you know where it goes. Another rumour that simply isn't true is don't use synthetic oils until your engine is broke in, that too simply is not true to the new oils.
Thanks for your information on synthetic oil .I like new info. The only thing to discuss now is price. Rotella from shell with a oil filter is about $40 . What is the price of synthetic with oil filter?
