Marc said:
Non-technical reasons? I doubt the manufacturer specifies an oil grade for their engines without consideration for the engineering that went into it.
And so therefore they recommend higher viscosity for essentially the same vehicle and engine going to other countries of similar climate.
The difference: We have CAFE requirements, they don't. You're going to tell me that that's not the driver behind the different recommendations on the same engine in the same climate?
As an aside, I will submit that the mfgr. doesn't understand as much as you or they think they do. If I had not been thinking outside the box on engine oil, my '99 2.7L would probably be in the scrap yard by now instead of running great. So, no - I don't always listen to the manufacturer.
And 10W40? Going out of the manufacturer recommendations to use higher-viscosity oil just because the warranty is over? On what basis? It surely doesn't bear repeating here, of all places, that by far the highest wear the engine experiences is on cold startup.
That's not everything. We have to look at the whole picture.
5W oil will pump faster on
cold startup and minimize the delay in getting oil to all the surfaces.
Certainly - important for very cold climates. I was mainly going for the 40 - the 10W just happens to be the more commonly available cold spec. in synthetics (i.e, it was secondary) for the higher top number. If they make a 5W-40 in synthetic, fine - use it - I have no problem with that.
For some years manufacturers have begun tightening clearances on their engines to reduce blowby and reduce emissions.
Yes. Though there are some here that have argued with me on that when I have stated same.
A wider spread of viscosity requires more additives, which can lead to more sludge and deposits in the engine.
I'm with you on that for *non-synth* -I reference the same info. every once in a while myself. But the same thing is *not* true for a synthetic, and since we started out discussing 5W-20, I assumed we were talking synthetics and I continued along that line. I almost stipulated that assumption on my part in my previous post, but decided it wasn't necessary - O thought ot was obvious. So I wil say it now - I was talking synhtetics. If you go with non-synthetic, then I would recommend against 10W-40 for exactly what you said about the unstable additional viscosity extenders that are needed. Better to go with mixing 10W-30 and 20W-50 - more of the former in winter, the latter in winter for an average of around 15W-40.
That may well be part of the reason for
the 5W20 recommendation.
So you push the second number down to 20 just so you can get the 5W...? For an extremely cold climate, yes. For milder climates, 10W for the cold startup should be fine. Certainly not worth pushing the hot number down so far just so the mfgr. can claim that for the CAFE numbers (which is the motivation as I pointed out as indicated by their specifying heavier oils for similar climates where they don't have to worry about CAFE).
At any rate, I'd want some hard data before going
outside the manufacturer's spec on oil on an otherwise healthy engine.
In a perfect world you could have all the data you wanted. In the real world, you have to make the decisions without the hard data. The laws of physics are the same around the world - I'd like to see the data that shows that the laws of physics somehow change when you have the same engine in the same operating temperature but it's within a different border.
You stay within the manufacturer's spec. - I'll go outside them. I have no problem with that. Neither will be catastrophic (unless you had a'98-'00 2.7, or certain Toyota engines, in which case you'd better
*NOT* follow the manufacturer's spec.), and we'll neither one be able to prove anything about the end result one way or the other. We both have the same info., we both make our own decisions and get the results as determined by the laws of physics which are immune to people's opinions and manufacturer's motiviations, i.e., CAFE.
Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my adddress with the letter 'x')
