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By peeeot - 16 Years Ago
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My '59 Galaxie's shop manual recommends 20W oil for the 292. I have googled and forum searched but have yet to find any clarification as to whether oil weight classification has changed since then. What I mean to ask is, does the oil referenced by the manual have some other modern equivalent? Like, 20W in 1959 = 40W in 2009? I find it hard to believe that what we today refer to as 20W oil was recommended back then, seeing as most modern engines with their tighter tolerances and such use a 5w-30, and only a few of the newest cars I've encountered take 5w-20. Thanks for patience with yet another oil-related thread! I know there are a ton of them floating around on the 'net.
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By crenwelge - 16 Years Ago
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Viscosity numbers have not changed. 20W is still 20W. However an oil with the API rating of MS, DG. was recommended. As far as I know, the only 20W oil available now is non detergent, which is certainly not what you want. Everyone has their own idea's about oil. If you are in a very cold country I would recommend 5W30, 10W30 for moderate temperature and 10W40 for warm climate.
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By timmy4 - 16 Years Ago
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I was told that you should not use 10-30 w oil in a engine with solid lifters because they do not put enough zink in the oil. A mechanic friend told me to use valvileene or mobile 1 with viscosity of 20- 50 which has more zink phosfate than 10 30 oil and the more zink is better for solid lifter engines.
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By pcmenten - 16 Years Ago
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I would use 20w-50, flows like 20w when cold, protects like 50w when hot. If the engine is an older rebuild or un-rebuilt, I'd use the Valvoline MaxLife. If you have a freshie, I'd use Mobil1.
In regards to 'Zinc', what the mechanic was talking about is ZDDP. We have flogged that subject endlessly. My take; buy STP Oil Treatment for 4 cylinder engines in the red bottle. Try WalMart. Use one bottle with oil changes.
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By paul2748 - 16 Years Ago
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My 2 cents - Use diesel oil 15/40 - enough zddp, don't need additive. Brands are Rotella T, Delo, Castrol, others. Same with something like 20/50 Castrol GTX
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By HT32BSX115 - 16 Years Ago
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Yes, we have flogged the oil issue pretty well.....It's still alive though.....maybe it should just be tortured regularly to keep it in line 
The amount of ZDDP is unrelated to the SAE weight.
Most people in the past have suggested using any diesel engine rated oil [CF or better] (SAE 30, 15W40, 40, 10W30 etc) because those oils have traditionally had higher levels of ZDDP.
GO to http://www.calsci.com/motorcycleinfo/API.html for more info.
There is a problem with the newest classification in that ZDDP is being removed (or the levels are being lowered) to save the cat converters.
ZDDP is not really needed in a lot of newer engines because they are equipped with roller cams/followers instead of flat tappets.
There's also companies out there that are producing ZDDP replacement additives. I don't how good they are though.
I had a look in my 57 Ford Shop manual and for the 292 it did say above 32*F to use 20-20W.
All I can say about what engines should use is that they know FAR more about lubrication today than they did 50 years ago.
I am going to run Chevron Delo 15W40 or Shell Rotella 15W40 in my newly rebuilt 292 (NOT the newest classification though)
(That's what the machine shop that built the engine told me to run in it.)
On the other hand, some of the oil refiners are starting to answer the question about older engines and ZDDP.
http://www.mobiloil.com/USA-English/MotorOil/Car_Care/AskMobil/ZDDP_Levels_Classic_Cars.aspx
Cheers,
Rick
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By peeeot - 16 Years Ago
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Thanks so much for all the info guys! I have Pennzoil 10W-40 in it now, but I'm going to start using Rotella 15w-40 on subsequent changes. It's surprising to me that so light a weight of oil would have been recommended from the factory, but as you say they didn't know as much then... I'm getting pretty awesome oil pressure with my 10w-40 at present; it was still 24 psi with idle so low the hot engine was hardly running. 
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By charliemccraney - 16 Years Ago
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The viscosity of the oil used has a lot to do with the engine clearances. With a freshly rebuilt, stock motor, I'd stay pretty close to the original recommendation. For a stock motor with some miles on it, a heavier oil should be alright. For a custom built motor go by the builders suggestion.
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By PF Arcand - 16 Years Ago
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The Pennzoil 10-40 is probably fine re ZDDP. Oils of that weight apparently have not had their zinc substantially reduced. Interestingly, our moderator Ted has reservations about using Diesel intended oils. If you go back a bit in the forum you will find his comments on the subject. This whole subject has been flogged to death & it takes patience to sort it out..
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