damian

iTrader: (2)

This is a VERY specific oil weight question, so please dont get into oil brands or synthetic vs non, et, et.

What I want to know is why one would choose to use 20w50 weight oil over 0w50 weight oil?

0w50 is going to give you better cold start up lubrication while maintaining good high temp operation. What is the drawback of using 0w50 over 20w50?

adam c

iTrader: (2)

Honestly, I don't think it makes much difference what weight oil you use, unless you live in an area with extremely cold winters. For the most part, oil companies offer lots of choices in weight for marketing reasons. They can claim to cover "all" of the markets if they have several products to choose from.

I suspect that you will not notice any measurable performance, temperature, or wear difference between the two oils you have mentioned.

quicksilver_rx7

http://auto.howstuffworks.com/question164.htm

Also:

http://en.wikipedia.org/wiki/Engine_oil

mad_7tist

common argument is that 0w50 uses more polymers etc. to get that broad of a rating. the polymers may breakdown so if you belive that then you would want as few as possible. you being in MN i could see it's place, me in hot tampa FL, not so much. again all you want is the lightest oil that will still give you proper oil pressures. something else will prob kill the car before an oil issue will. assuming the pressure is still in spec.

damian

iTrader: (2)

hahah, thanks for the links quicksilver, but I know what the oil weight mean, i am looking for real world usage comments from us rotary heads.

damian

iTrader: (2)

well i do live in a place with extremely cold winters (minnesota) :-)

...but more importantly I need to account for track level usage of the car, yet not eat it up during cold start up, and i do believe the weight oil i choose will make a difference.

damian

iTrader: (2)

so let me just clarify, in your opinion there isnt any significant difference in using 20w50 vs 0w50 in terms of wear due to being to thick at cold tempratures during cold start up?

quicksilver_rx7

Damian,
I wasn't questioning your knowledge of "how oil works", but they do go into detail about the different weights and viscosity in reference to climate and usage. I'm not really sure if the question that you're asking is one that can have a direct answer because of all the different variables that affect usage.

One of the major variables is, how far into the fall or winter season do you track? Obviously, it's not as much a factor during the summer months because you could technically run straight 50w oil and be fine unless the whole thermal pellet thing bothers you. Other than that, you're only option is to find a balance like 10w40 for the winter months unless you want to cold start with thin oil, and change to thick oil after the car is warm. I just think that anyw50 is too much for a cold climate.

Joe

XSrcing

0w-50 does use more expansion polymers to get the rating. 20w-50 doesn't need as much because it already starts off with a higher viscosity rating.

and yes, heat breaks the polymers down and can cause your oil to lose viscosity when subjected to high heat (like inside a rotary).

this is why redline and such offer single weight oils for racing purposes.

damian

iTrader: (2)

>>I wasn't questioning your knowledge of "how oil works", but they do go into detail about the different weights and viscosity in reference to climate and usage.

hey i appreciate it all, i have no ego with this stuff, im trying to learn as much as i can to make the most informed decision :-)

damian

iTrader: (2)

>>unless the whole thermal pellet thing bothers you

what part of it would bother me? I am going to be using the pellet mod part when i re-assemble the engine so that it always flows oil, as well as a race oil regulator to maintain reliable oil pressure.

GooRoo

iTrader: (4)

This is true for non-synthetic oils, but not for most full synthetics. The properties of synthetic oil make it possible to get wide weight range oils without adding the polymers.

Some links from google backing this up

note: It is important to note that what is a 'synthetic oil' can change according to the standards bodies. So it's hard to say without mentioning a specific product whether or not it is a 'full synthetic'

http://www.bobistheoilguy.com/motoroil.html
http://www.yft.org/tex_vfr/tech/oil.htm
http://www.mobiloil.com/USA-English/...rade_Oils.aspx
http://www.realclassic.co.uk/techfiles/oil030319.html
http://www.xs11.com/stories/mcnoil94.htm

adam c

iTrader: (2)

Your engine will fail from something else, far before whatever oil you choose makes any difference. When was the last time ANY engine failed due to oil related issues? Running out, or not changing it doesn't count

Don't beat yourself up over this. It isn't that critical.

GooRoo

iTrader: (4)

Just to throw my opinion out here...

For break-in, I ran Dino. It allows more friction to wear the parts in, and is cheaper, since you have to replace it quickly anyway. 10w30/10w40 whatever, no boost low load driving will work with most anything.

Once I was broken-in, I ran full synthetic.

On the low end, I think you run the low weight as low as possible. All oil weights are too thick at startup to lubricate properly, so run 0W if possible.

On the high end, run the minimum weight that gets you proper oil pressure. The lower weight oils will flow more at a given pressure, and flow is what keeps parts spinning in their proper orbit.

At this point most things I've read say max pressure should be about 10psi per 1000 rpm in a piston motor, and I don't see why it would be different in a rotary. I believe the manual says it should be close to 20-40psi at idle and 70psi by 4000 rpm. Draw your own conclusions here.

In any case I would approach the minimum oil pressure from the high side and be careful to make sure you are safe. On street cars I would expect this number to be between 20 and 40. For a track car I might try 50 if the oil pressure at high temps is not staying high enough, or I wanted to run greater oil pressures to keep parts working at high load.

In my car right now I'm running 5w30 Redline. Oil pressures seem to be ok, but I may try 0W40 next to see what the difference is.


So, to answer the original question, I would use 0w50 over 20w50 because the flow at low temps would be better. This assumes 50 is the proper weight to get the desired oil pressure at redline.

GooRoo

iTrader: (4)

He suspects that oil may have played a role in both of his bearing failures... I am not convinced either way at this point.

damian

iTrader: (2)

good point by all, just to be clear, i am including oil weights as somthign to look at in the bearing failures, however, not nessicarily making any changes yet. one thing to concider is that my track car ran an entire season of over 20+ track events (in 2004) with no bearing issues. either way, I want to explore making lubrication changes that may help the car if there are things i can improve on, even if they are unrealted to the bearign failures.

mad_7tist

to be safe a good oil temp sensor would be nice to have. also i know the need to search for a reason as to the bearing failure, but sometimes things break, not due to any major problem. it is a tracked car. more of an issue of what and when something will break. another good question would be what would some other experienced engine builders consider correct oil temps and pressures during an event and at what rpm. that would be the correct gague as to what weight oil to run. if 10w30 got you to the target oil pressure and temp for example running any mix of 50 weight would just cost HP.

FLA94FD

I agree, If I had a track car I would find out what team Mazda runs. For the most part I don't think it will make that much of a difference. Most of it's hype there all so close that something else will fail you can blame on what you want.

diyman25

FOR ME I always use 20w-50 on my Race CAR. On rotary using 20w-50 dont seen to affect engine that much. I rember on my friend Z06 once we change to 15-50, yes we got super high oil pressure, but the engine also rev much slower...

For a Tracak car, I recomand using 20w-50... if you are worry about cold start. you can install a accsump is a good divice to have it any way, and when you want to start the car at cold, just warm the sump( using a hot tower or heat bag) and prime your engine by open the valve .. ( this how they using on the Dry sump motor... )

David Beale

Do be careful copying what race teams use. They may build the engine to run a specific oil - adjusting the oil pump and pressure regulators.

On the street, using "normal" oil, not synthetics, I've found the wider the range, the more prone the oil is to viscosity breakdown. My 2001 Pathfinder (a dredded "gas gusling" SUV), specifies 5W30. My information is they went to this to improve the fuel consumption results. I found it broke down and changed immediatly (first oil change) to 10W30. The 10W30 has never broken down. Note that my indication of viscosity breakdown is a rumble heard when a hot engine is allowed to idle and/or seeing loss of oil pressure on a gauge. I believe this rumble is at least one bearing loosing the oil film. Note also that I live in a similar climate - I'm in the "great white north". I have used 5W30 in winter in another vehicle, but stopped when I noticed it broke down when I travelled to the west coast (at an ambient temp of 35F - it rairly gets that warm here in winter).

I -think- you want a thiner oil in a turbo car, to ensure the turbo bearings get enough when you start up. I run 10W30 Pensoil in my car - but it's street only.

More info - I switched my Pathfinder to Mobil 1 10W30 once I was sure it was fully broken in - and the improvement in mileage paid for the extra cost of the oil twice over! I haven't tried synthetic in the car - not sure there would be any benefit to paying more considering how often the oil gets changed.

As far as synthetic vs conventional, as far as I know, if you are considering 0WXX you are talking about synthetic. I've never seen 0WXX in conventional oils.

DamonB

Right. And longevity is not their main goal either.

Your oil is fine. IMO this is one of those "the sky is falling!" cases. From listening to people on this forum you'd think my car would blow up the first time I put the throttle to the floor with my stock oil coolers, stock turbos, stock intercooler, stock radiator, surely stratospheric intake temps etc and yet I beat the crap out of my car constantly with fewer issues than most people here.

Your engines get run hard at sustained RPM. Are you running stock bearings or the clearanced race bearings? The race bearings allow much more oiling to the journals because they have bigger grooves. They are also set into the rotor with set screws to prevent them from spinning. A failed bearing often times is indicative of an oiling problem, but it's not the oil itself IMO. I'd investigate pickup issues and what types of bearings are in the engine.

Here are Mazda Motorsports thoughts on bearings:

http://www.mazdamotorsports.com/weba...t=rotorbearing

http://www.mazdamotorsports.com/weba...ct=mainbearing

Kento

I'm late to the party, but I thought I'd throw out some of my opinions/knowledge :

Some of this was discussed before in a previous thread a while back regarding running ultra-lightweight viscosity oils in a rotary. Don't have it here at the moment, but I'll try and dig it up.

The reason you don't see dino oils in ultra-lightweight viscosities is because dino oils depend on the base stock upon which they are built, and there are no 0W or 5W base crude stocks. Synthetics on the other hand can be manufactured in whatever base stock is desired. This is why it is not recommended to use dino oils with a large gap in the multi-viscosity rating, because a lot of polymer and other viscosity improver additives are added to the oil. The more additives you put in an oil, the less room for the actual base stock oil.

While the point that lighter viscosity oils provide better lubrication on startup is true, there's a couple of caveats to that view. Much of the "better startup lubrication" is dependent upon the actual clearances of the bearings, the oil pathways, the blow-off pressure release point, etc.; manufacturers recommend a certain viscosity to cover all the possible situations, which include an owner simply firing the car up cold and taking off. A 10W or 20W multi-viscosity oil also has superior film strength and retention to a 0W; in other words, it doesn't drain off parts as easily, and the film that's there right at startup is stronger.
It's also been found that synthetic ester base compounds (the most expensive synthetic oils to manufacture, unfortunately) have a polar effect; their molecules actually attract and cling to metals, so startup lubrication is assisted in that area.

My main concern with running 0W oil in a rotary is that its demands on the oil are a lot different than with a conventional gasoline engine. Conventional engines don't have internal rotor gears and eccentric shafts which shear the oil molecules apart, which can quickly reduce the actual viscosity of the oil. Sure, there's plenty of manufacturers who recommend 0W oils in their latest cars and run them for long distances before oil changes, but again, those engines are different, and they've obviously done exhaustive testing to ensure that the 0W viscosity doesn't pose any problems (the main reason for 0W oils as an OEM application is for EPA fuel economy regs anyway). Unless you are changing the oil after every track day (and even then, I'd still be hesitant), I'd have major reservations about a 0W's ability to maintain its lubricative abilities even after a short period of time. (IIRC, in the other thread, one poster who spoke to a Formula Mazda engine builder said they must do complete rebuilds every race. Whether this is the result of their using 0W oils is obviously open to question, but the fact is there.)

Kento

Oh, and I agree with Damon: I doubt that the bearing problems you experienced can be blamed on using a 20W50 oil.

dubulup

Rick Engman only recommends 20W50 for rotaries...he's been building (anything from race 4 rotors to street 2 rotors) for a long time

Sgtblue

iTrader: (16)

Wow. Good thread.