what's the thickest oil weight to run?

[ChevelleSSLS6]

Put in about a cup of lacquer thinner in the oil. It will soften and swell the seals. There are off the shelf additives available as well, but they use the same stuff/concept.

Seems to me this would thin out the oil... maybe lacquer thinner+lucas/15-40 oil?

Or would ya run it like that for a few minutes at idle like the 'engine clean' stuff then do a LOF and it'll allow the seals to 'limp leak free' for a few more miles?

 

[ChevelleSSLS6]

also- I do believe JASO-MA oil (cycle oil) has higher zinc content... with the new formulations of whatever letter they're at now- L, M?

GM does (or used to offer) zddp additive, make sure to shake the container WELL before using, or the good stuff will sit at the bottom and you'll dump the 'filler oil' in the crankcase.

Diesel oil does not offer the zddp levels that it used to with the new emissions garbage. Thanks EPA!

 

[Davinator61]

My understanding is that on older engines, a 10W40, 15W40, or 20W50 would suffice, depending on your Ambient Air Temperature Range, Driving Conditions, Driving Habits, and Overall Engine Condition. However, I, personally would not use anything heavier than a 20W50, even a Full Synthetic like Amsoil or Royal Purple, as the oil needs to be thin enough to be pushed into the Engine's Oil Galleries by the Oil Pump without Grenading it in the process.

But what the Heck do I know? I'm Just Spouting an Opinion While Standing on My Soapbox as This Subject, once again, Gets Beaten Like a Dead Horse.hasta

 

[Ecomike]

My understanding is that on older engines, a 10W40, 15W40, or 20W50 would suffice, depending on your Ambient Air Temperature Range, Driving Conditions, Driving Habits, and Overall Engine Condition. However, I, personally would not use anything heavier than a 20W50, even a Full Synthetic like Amsoil or Royal Purple, as the oil needs to be thin enough to be pushed into the Engine's Oil Galleries by the Oil Pump without Grenading it in the process.

But what the Heck do I know? I'm Just Spouting an Opinion While Standing on My Soapbox as This Subject, once again, Gets Beaten Like a Dead Horse.hasta

We use to run straight 40WT all the time before multi viscosity came along. Racing engines used straight 50WT at one time. The biggest issue is start up viscosity. I would not have a problem running something like 30W60 if there was such a thing, on an old engine. There was one guy on here running straight Lucas in his well worn engine.