I've been reading a lot of oil threads and it seems like people are tired of arguing the same points over and over but i haven't been able to find anyone with the same problem i have.
So i was wondering if you all could help me.
I have a 1968 corvette that was built into a street rod in the late 90's but it was only driven a few times a year since then,a a total of 4300 miles. Its a 350 corvette engine that produces 450+ horsepower (based on a hp calculator and a few races with a 09 m3).
It needs a valve job, it smoked out of the drivers side and i constantly had to top off the oil before i went for a drive.
i was using 10w-30 and after driving it for awhile (500 miles over 6 months) I noticed the oil became pretty dirty but as a result the engine stopped smoking and i did not have to add any oil to it even after 3 or 4 drives.
So im thinking if the oil is heavier, the smoking with decrease? Im wondering if 20w-50 would be a good choice for me for awhile before i decide to sell the car or get a valve job.
I live in southern California, i only drive the car 2-4 times a month in temperatures ranging from 65-80. The engine has 5,000 miles on it. When i do drive it, i drive slowly until 190 degrees then i drive it very fast and hard.
Are there any negatives in using 20w-50 in my situation? What would you recommend?

 

with that low miles you may have just seated the rings, really hard to say what was going on.

If its not smoking now don't change what your doing. You really should run the recommended oil for the car which is usually 30WT.

Stay with 30WY if you can, 20W50 is heavy for that service unless the engine was built for the heavier oil.

Neal

 

Heavier oil just sucks power from the motor and makes the oil pump/diz gear work a little harder. Unless it was built super loose theres no need for thick oil.

 

How do you know?

 

10W30 will get to the top of the engine much faster than 20W50 on a cold start. Most of the engine wear happens in the first few moments of operation, before the oil has had a chance to get anywhere. The remainder of the wear happens between then and when the engine is fully warm. Oil and water, both. Don't flog a cold engine. Not if you want to keep it. For that same reason, you need to run at least a 180 degree thermostst. IMHO, a 160 is not hot enough.
If your bearings are so sloppy that you need heavy oil to get any oil pressure, it's time for an overhaul.

 

Go with 10W-40 and the smoking could be a lot of things. Not likely you need a valve job with under 5000 miles. Could be valve seals. If not could be as minor as an intake gasket leak or missing or poor baffles at the valve cover, bad PCV valve, poor ring seal, head gasket, cracked head, stuck rings from sitting. Best off doing a compression test and a leak down test to isolate your problem or at least eliminate issues. If compression and leakdown is good my money is on a leaky intake manifold gasket sucking oil into the intake on the intake stroke. This happens a lot on new builds and many times is not caught right away and is a couple hour low price fix.
.

 

If you run too heavy of oil in your engine, meaning the molecule are to big for the application.

The engine it's self will shear the molecule down to the right size.

You will end up with large molecules and pieces of molecules for oil.

Ralph

 

do you have a roller cam? if not,then you need an additive,todays oil is bad on flat lifters. the zinc content is very low. i use sae30 with a bottle of delco engine oil supplement. i mix up 5qt at a time so if i need to top up i am assured of having the proper stuff. i buy it from the local chevy dealer, buying a case of 12 drops the per bottle price to $6.15.