Whos using 15W40?

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Originally Posted By: sirgerman
until what winter temperature i can still use 15/40w diesel in my Saturn ?

In California? Until the sun burns out, I suppose. My Audi called for 15w-40 down to something like -15 C. Like anything, it's application dependent.
 
I used 15w40 in my Scirocco for one OCI a couplle of years ago - it was about 3AM on Christmas Eve., and I split my sump on a speedbump about 100yards from my house.

Killed the engine, rolled into my parking space and left it till daylight.

Being Xmas eve, nowhere was open so I dropped the sump and cleaned it and welded up the split, threw it back on and filled up with the only oil I had to hand which was a Mineral 15w40. Fuel Economy was marginally reduced but it still cranked and fired up without any lifter noise or anything.

I just cant help but think that with my cam, spring pressure and shimmed, flat tappets, I need a decent film thickness and lots of zinc/moly/ws2 in there.. and I *FEEL* like 10w is the best comprimise of flowability and thickness.
Putting a micrometer on my cam lobes, and putting an internal vernier down my cylinder bores both back up my thinking
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Originally Posted By: Olas
Putting a micrometer on my cam lobes, and putting an internal vernier down my cylinder bores both back up my thinking
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How does that show a 10w-XX of any sort is actually optimal, and in comparison to what? I tell you right now that if you had a 10w-XX anything in a vehicle outside here right now, unless everything was in peak condition and you had a lot of luck on your side (and a working block heater), you would be leaving it sit there for the next week or until the tow truck showed up, whichever comes first.

This isn't a thick versus thin thing at all, but I rarely use a 10w-XX anything. The F-150 has it, but I don't need to do any measurements to determine there's no wear. It hasn't moved in ages.

If one wants a 40 grade, there are better options than 10w-40 in conventional or synthetic. There are better options than 10w-30, too. 10w-XX has jumped the shark, and that's beginning to be apparent in diesels, too, with 5w-30 and 0w-30 HDEOs.
 
Garak - measurements don't prove that anything is optimised but I feel like they show that my lube choice isn't causing any damage..
I thought that too thick an oil wouldn't get to the valvetrain quick enough and allow wear, and because I can't see or measure any wear the 10w must be sufficiently 'liquid' to get where it needs to be in a short enough time that no wear is taking place.

What is the outdoor temp. in Saskatchewan at the moment? Its around 8 or 9C where I am and the coldest winter I remember it got down to about -14 or -15C, 'Rocco still cranked and fired in those conditions and I don't remember it being any noisier than it usually is.. All anecdotal, but humans are funny like that
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Originally Posted By: Olas
Garak - measurements don't prove that anything is optimised but I feel like they show that my lube choice isn't causing any damage..

Absolutely my point. 10w-XX may certainly be doing the job, but it's hard to try to claim science unless you do more than one engine and many, many viscosities.

Originally Posted By: Olas
What is the outdoor temp. in Saskatchewan at the moment?

Right now, it is a balmy -32 C.
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In any case, don't get me wrong. I'm not all fired up that a 0w-XX is necessary in this climate (or yours). Heck, me using a synthetic is an anomaly in the first place.
 
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