Oil Type

[msass]

What is the best type of oil to use for my '51 Henry J?

[BigDave LM6174]

Where are you? What climate?

[msass]

Northeast Iowa although not planning on driving it in the winter.

[Fid]

There seems to be a lot of opinions on this. I live in Minnesota and only drive my cars between April and Oct. I was told years ago by a seasoned mechanic to run only straight weight oil in the older engines so I always run/ran Valvoline SAE 30W in my cars. Started this practice on my '53 J back in '72 when we rebuilt the engine. Forty years later, it runs great and does not smoke and has 30,000 additional miles on it so using the straight weight has worked out quite well on that car. I do add zinc to it now as modern oil does not contain zinc... although I've heard you can buy oil that does. I should note that I change the oil every 1000 miles or less depending on how clean/dirty it gets.  The old flatheads like the J, which do not have an oil filter (at least most don't and those that do really do not make any difference as it's only a by-pass filter and really doesn't clean the oil the way a modern day filter does) should be changed about every 1000.
This practice has worked well on my cars for years now.

[BigDave LM6174]

Fid, 30 weight detergent or non detergent?

[Fid]

Detergent - but that's only after knowing the engine was rebuild and everything was cleaned / boiled out. Yes, if it were an old, non-rebuilt engine with unknown maintenance history, you would want to consider using non-detergent oils as detergent oil will loosen up deposits and gunk and start circulating it through the engine which can cause problems.  But if the engine is known to be clean inside, you can run detergent oil in it.

[joefrazer]

My latest purchase, an early 47K shows evidence of having detergent oil used recently. The pan was full of gunk that was obviously loosened by the oil's additives. The good news is that the engine is clean inside, the downside is that it took me an hour to get the pan cleaned out!

[msass]

So is it pretty unanimous that people use SAE 30W?

[retired wrench]

  I always ran 20W in summer and 10W in winter. 30W gets pretty thick to push thro a .002 gap if it gets cold,and your engine is running dry for quit a while.

[Logan]

What is the rationale for using straight weight rather than multi viscosity?  It seem like if you had the right additives (or lack of them), all things considered, multi would be preferable.  Reasons for going with straight weight?

[boatingbill]

On a hot summer day check oil pressure at idle using 10w30 after an old engine is fully
warmed up. Then repeat this with straight 30w. The straight weight will hold  pressure
better on an engine with worn internal parts.