zoom44

he's never going to see temps where the thickness at low temp is a problem. That 0w is going to be too thin at the temps he normally runs in to keep the bearings lubed at start up.

He's not an FI team running a race car in Europe that will build a new engine soon and goes with the 0w for fuel savings. He's not driving his car in Germany summer or Winter.

Tropics.
This car will not ever see 15 degrees unless he drives it into the walk in of a Restaurant.

REDRX3RX8

Ok, what Mazda tells us to use would be like Mobil Clean 5000 5w20 which is 47.8 Cst @40deg C (104 deg F).

Other countries use 5w30 which would be 62.2 Cst @ 40 C.

Even 10w30 is 68.7 Cst, but Mobil 1 0w40 is 75 Cst @ 40 C.

75 Cst compared to 47.8Cst means that 0w40 is thicker at startup than 5w20.

What I'm saying is that in the tropics it might still be 60F when he starts which is 60F to 180F or a difference of 120degrees.

My 8 and many others always have summer tires on, so I don't even start it under 40 deg F, which only adds 20 deg F difference.

Mobil 1 is not a racing oil, but can be used as one; racing oils usually have max ZDDP for camshaft lubrication which will kill a cat, and we don't even need the normal ZDDP level that's in any of these oils used in street cars.

zoom44

now how about a 20w 50?

edit: quick look on bitog

Dino
Valvoline 20W50: cSt @ 40°C 170.9, cSt @ 100°C 18.5

or synth 15w 20

Mobil1 15W50: cSt @ 40°C 131.2, cSt @ 100°C 18.1

i'd be using one of those in the tropics. Even in Florida we have been recommending it for years and everyone has had good results.

I know Jeff was concerned at some point about amount injected by the mop when using 20w50 but most people switching oils are also doing some premix like swoope.

PhillipM

0w oil will never be too thin.

Even in very hot climates 0w is at least twice as thick than you ideally want for protection/flow at startup.
In cooler climates it might well be 10 times thicker...

As Red has noted above, some 5w oils may be thinner than the 0w oils depending on the manufacturer/type of oil, because they go through the rating in the same viscosity band, just with depress pour points to gain the 0w rating, so do your research before buying.

zoom44

how could that be? if the normal weight called for(in your region) is 5w30 and you use 0w20 you think the 0w20 is not going to be too thin? what if the normal weight called for is 10w30? of course there is a point where some 0w is too thin.

i agree that the 0w40 might be ok but a 5w or 10w would be better in the tropics and a 50 would be better still

edit- never mind answered my own question. 0w wont get too thin in his case because it will be acting like a straight 40 most of the time.

id still recommend something in a 50 and to buy cheapest and most available.

REDRX3RX8

Thanks for more info.

Oil #'s frequently confuse, but the best way to look at it is: what viscosity do I want at operating temp; most bearings like about SAE30 or 40.

Ok, then, how much thickening will I tolerate over night?

The best way is to compare specs, but you can guess a little, buy noticing 20w40 is thinner than SAE40 the next morning.

10W40 is thinner, 5w40 can be thinner, and 0w40 should be the thinnest.

The 0w40 is made different than those older oils, too; it's weight is what it is without massaging compared to the old #'s.

Whereas, with 10w40 they took a SAE10 motor oil, and added VI improvers (STP) to get the operating temp weight up to SAE40.

That worked, but the VI could shear, and the leftovers could make hard carbon.

PhillipM

^^edit: beat me to it.

0w30 is never too thin compared to 5/10/15/40000w30
0w20 is never too thin compared to 5/10/15w20
Neither is 0w40, 0w50, 0w60....
It's always a benefit in terms of flow and wear protection.

However, if you're going with something with a wide range such as a 5w-50/0w-60 then make sure it's got a decent basestock, as a lot of cheap VI modifiers with a mineral basestock will break down pretty quickly under the shear loadings in the rotaries' stationary gears.
I'd still like to see the EOA from some of this for those that like their 50w though, I think it may do very well:

http://www.millersoils-online.co.uk/...d=9195865_1509

REDRX3RX8

So Phillip, what do you do in the motherland?

You understand oils, and if a 5w20 can run in the renesis, 0w40 is quite a bit thicker at any temp.

Lots of people have run 20w50 in rotarys, and I don't think they are necessarily too thick.

I looked up tests where they ran many different brands and weights like 0w40, 5w40, 15w50, 20w50 etc. to compare horsepower and torque in a v8 engine.

It seemed that the Mobil 1 0w40 had the best hpr, and maybe lowest fluid friction, so I also based using my 0w40 like on that test.

I'm thinking that 0w40 is a gas saving oil for high performance cars compared to those thicker weights that are hpr robbing.

The goldilocks oil weight!

PhillipM

Build things that go vroooom usually.
Personally we always run a decent synthetic 0/5w-30, the extra cooling alone outweighs cheaper/thicker oils for us, and the slight power improvement over a 15w50 doesn't hurt either, but we don't have any problems with viscosity loss - although it is changed fairly often (it has to be, the engine's out every other week :D )

REDRX3RX8

There you go, bearings can run hotter with a too thick oil.

Hey, wait until they make an oil that thickens even less at cool down than 0w30 or 0w40.

They'll call it 00w30 or 00w40, and people will really get confused.

PhillipM

I've got some oil here for the car which is 12cst (yes, twelve) @40*c, (And a VI of ~470...) looks like someone's made a really weak cup of black coffee....
Lovely stuff, looks like water, but get it on your hands and you can't pick anything up for a day

bse50

Oil brand?

PhillipM

Silkolene, you might have noticed I like Silkolene

nycgps

iTrader: (1)

15/20w50 oil here. no issue.

if I race my car and overhaul the engine every week or 2, I probably go for less.

when it gets warmer im gonna take the FC engine apart and look at it, I know its not the same car but most parts in the engine(or rotary, in general) has not been changed) good for comparison.

I can tell the previous owner abused the crap out of it. he said he put only 5w30. It was a rebuild engine now with 30K miles. lets just see how it goes.