The Stovebolt Site Forums The Shop Area Engine Shop What type oil? (preparing to start 235 Chevy engine)

I have an original 235 Chevy engine that I am preparing to restart after many years of idleness. To my knowledge the motor has not been rebuilt. I’ve seen several opinions advocating for the use of 10W-40 diesel oil in these older engines. Would it be better to try and seek out and use a non-detergent 10W-40 diesel oil (if there is such a thing) or would a modern detergent oil be ok? I’m inclined to go with a non-detergent oil and look forward to the feedback of the group. Thanks in advance.

If it hasn't been rebuilt, I wouldn't bother with break-in oil. Any modern oil should be fine. I'm planning on adding some ZDDP when I restart mine (I did have to replace one lifter.) Otherwise, I plan on using some Valvoline VR1 10w30 I got a good deal on. Otherwise I'll use 15W40 diesel oil that I use on my daily driver. I do have a bypass filter that'll be on it.

its been siting a long time. I am of the opposite opinion on the brake-in oil. I would use brake in oil because it has additives that are intended to almost super lubricate the parts enough to allow them to mate on initial run in without failing. Seems to me that something like that may be helpful to a motor that has been sitting for a while and may have some rough edges internally. With parts and machine work at such a premium these days, why not give yourself every edge to successfully start this motor and keep it running.

I have had very very good outcomes with the Brand Penn 30 wt. Brake in oil (now called Penn Grade 1 but its the same exact green Kendal ! oil its always been).


https://penngrade1.com/products/high-performance-oils/penngrade-1-break-in-oil-sae-30/

Does your engine have a filter? If so use modern detergent oil.

I have a friend with a large car collection that includes many cars from the teens through the 1930s with original, unrebuilt engines. Most of them do not have oil filters. He will absolutely not use detergent oil in those vehicles.

In the case of vehicles with filters and/or rebuilt engines, they all get detergent oil.

In simple terms, the reason for using detergent oil on an engine with a filter is detergent oil suspends solids so an oil filter can filter it out. With out a filter, the suspended solids continue to circulate thru the entire oil system, bearing included. With non detergent oil, solids settle out to the bottom of the oil pan so it can be drained out.

"Non-detergent" multi-viscosity oils do not exist. The above comments about detergents holding contaminants in suspension is correct, but the actual reason for them is different. Detergents grab onto and hold particles TOO SMALL FOR THE FILTER TO STRAIN OUT. Those contaminants are held in suspension and dispersed by the oil so they don't form large clumps, and they get drained out with the next oil change. An engine that has run non detergent oil for a long time might require several oil changes before most of the sludge it contains is cleaned away. You can "de-sludge" an engine by adding a heavy dose of Diesel fuel to the oil for a few minutes before changing the oil, but don't drive the vehicle- - - -moderately fast idle for a while, then drain the hot oil/Diesel mix and most of the sludge will go with it.
Jerry

When I pulled the engine out of my truck, the sludge in the pan was unbelievable, I don't think any amount of solvent or run time would have removed the majority of it. I removed all of the tin, scraped and degrease as much as I could, then more degreaser and a pressure wash. I put it all back together with new gaskets and seals. I disassembled the oil pump and cleaned it also. It doesn't smoke or use oil other than the rope rear main seal. I use 5w-30 or 10w-30 synthetic 'cuz I keep a bunch of it in stock, engine runs 38 psi oil pressure hot at 3750 RPM.

The trick to the solvent run is to overfill the crankcase by 2-3 quarts to the point that the crankshaft and connecting rods are running partially submerged in an oil/solvent mixture. The rods dip into the solvent mix about 40 times a second at 1500 RPM. Try taking a ride in a commercial washing machine sometime for a similar experience to getting power washed by hot, splashed solvent for 20 minutes or so. Then try doing the same amount of cleaning by hand with a parts washing brush.
Jerry

There is no oil filter on the 235 engine.

Thank you

Pulling the engine to de-sludge it was only one of the reasons, I knew it needed a new camshaft due to 2 lobes with no lift, also it needed a new clutch. I didn't even consider trying a solvent flush knowing the engine was coming out. Once I had it out of the truck it was a no-brainer to pull all the tin for inspection. Overfilling and solvent would have scoured some of the garbage for sure but I am glad I didn't run that sludge laden mix through the bearings. I agree, washing parts by hand is a tedious dirty job, the pressure washer made it bearable.

I went ahead and dropped the pan on my 62 C10. I was very glad I did ! The sludge was probably close to 3/4 inch deep.
While the pan was off I got a good look into the crankcase. I was surprised. Other that the sludge in the pan , it was very clean. Almost new looking. This forum helped me find out the engine had been replaced at some point with a rebuilt one 👍