There's a discussion happening on M.nut. I hate everything over there. You guys know better than them.
the nc2 Miata in 2009 has 5-w30 on the oil cap. In 2011 or so, they started recommending 0w-20. Nothing really changed engine internal wise. I've never changed the first number of viscosity. Only the second set of numbers. What say you chums?
Only reason I ask is my other cars take 0w20. It would make oil changes a lot simpler to buy bulk of the same oil.
The important number is the second. The 0W is how the oil behaves at cold temps. the second number is the oil at operating temp, or more importantly measured at 100*C.
A SAE 30 should fall in the 9.5-11cSt range where as an SAE 20 will fall in the 7.5-9 cSt range. If the car is calling for a 30, I'd not go thinner unless you are running it in colder temps.
Hmm. Living in the high desert presents a challenge. Winter time it's sometimes negatives. Some days a high of 60° in the winter. Summertime, you can have a 100° with a low of 40.
I have seen sometime where they change a spring in a regulator or change an orifice or drill a hole a different size in the block to accompany the viscosity change, so it may actually be different internals.
I have also seen manufacturers change to a thinner oil just for MPG/emissions reasons without changing a thing, but in those situations, they have done pretty significant testing to make sure it's A-OK. Perhaps they realized that the oil pump carries a surplus of volume and the lower viscosity doesn't have much effect.
The important thing is not so much oil contact surfaces like rings or rockers/followers, but in the bearing surfaces. The clearances are engineered for a specific viscosity and pressure - the point is to always have a pressurized film of oil that suspends them and doesn't allow metal-to-metal contact. Going thinner and maintaining pressure is not always a sign that things are kosher. The overall average oil pressure may look good, but oil that is too thin will squeeze out of the way during higher forces. The gauge might tell you 40 psi, but it's hard to tell what is actually happening at the bearings.
The old school race trick was to run thinner oil until you notice a drop in pressure, then go back up one weight and compare oil temperature. If temps don't rise, they called it good because they assumed the oil wasn't getting squished out and therefore friction wasn't spiking. I never understood that logic, though, because if oil temps DID rise, it meant it was too late and they probably needed new bearings.
In reply to Curtis73 :
YEAH, being in the oil business I've heard so many "old school tricks" that were just crap.
_ said:Hmm. Living in the high desert presents a challenge. Winter time it's sometimes negatives. Some days a high of 60° in the winter. Summertime, you can have a 100° with a low of 40.
I would say you should definitely NOT go thinner. 5w30 is good for an ambient temp range of about -30F to +95F
If you did a 0w20, that would be more applicable for a temp range of -40F to about +70F. Unless you live in Alaska or Siberia, unlikely that 0w20 would be a good fit.
The important number is matching the cold-rated weight to your ambient temps and the hot-rated weight to your vehicle's system. For most vehicles, there isn't much difference in peak oil temperatures regardless of what's going on outside. If you drive a vehicle for 20 minutes in winter or summer, the oil temps won't be much different. The engineers did a fantastic job of engineering and testing for you, so you should keep the same hot number and adjust the cold-rated number to suit your climate.
In reply to bobzilla :
Yes, I once cut down a piece of my belt to make a rod bearing. It worked, for a little while.
Personally, with that much variability in ambient temps, I'd run a good 0w30.
Normally, I say:
If it says 5-30, use 5-30!
However, just like anything else I guess you might want to make a different decision than the factory engineer because you prioritize a different parameter. So what are you trying to optimize?
In reply to Robbie :
Hey I can only blame me if I put too thin of oil in and something let's go. If it was a no brainer then I would be switching to buying bulk 0w20, instead of two different viscosities.
I can't confirm what the filler cap says, but the 2009 owners manual states 5W20 (not 5W30) in all North American markets and the 2012 owners manual calls for 0W20 in USA/Canada or 5W20 in Mexico....Sounds like a cold-start/EPA motivated call to me. The 5W30 only comes in for (hot climate) Mexico as an approved alternative if 5W20 cannot be sourced. Since they're both 20 weight, in my non-professional opinion I don't really see any reason to go for the 5W over the 0W.
A lot of times the only difference between North American market and Euro market was the label saying what grade oil to use.
Personally I like thinner oils, because the main thing the oil does is pull heat out of the bearing, thinner oils flow more volume for the same pressure, meaning more cooling. As long as it has decent hot oil pressure at idle, it's good. I like the modern 0W- oils a lot, I used to run 0W40 in my S40. Oil light would flicker when idling hot with 5W30, which the owner's manual said was normal and just hold the engine speed up a bit until it cooled off. Orrrr... I could run 0W40 and be fine.
The only real counterexample to this is, of course, Mazda rotaries, because the oil pressure regulator is before the engine but after the oil cooler. Thicker oil in a rotary means more oil goes through the oil cooler than through the engine, so oil temps decrease as a result.
Pulling heat out is definitely one thing that oil does. But I'd say the main thing it does is provide a fluid film to keep the metal parts from contacting each other and tearing themselves apart. And for maximum effectiveness there you more or less want the thickest oil that the clearances can tolerate. I'm not saying to run 20w50 in something spec'd for 0w20 or anything crazy like that (because chances are the tolerances can't handle that)...but I personally wouldn't run 0w20 in anything, even if it's what the label asks for. Granted, that's for me and my tendency to drive things hard, even my daily driver. Though IIRC the OP is planning to autocrossing the NC in question so I'd say that logic applies here. If it's a typical camry or similar that will never see more than half throttle you could probably run literal water (not to be confused with 0w20 oil which aside from the color is an easy mistake to make) and be fine for a while. It is definitely correct that the hot viscosity is the most important, but the rule of thumb I've lived by is "the thickest oil that will cold start well" and it hasn't steered me wrong yet. 2009 might be out of range for this, but at least since the Obama-era EPA restrictions the manufacturer's priorities when it comes to speccing an oil, in order, have been: fuel economy, fuel economy, fuel economy, and engine durability. So the engineers' design priorities are likely different to the vehicle owner's operational priorities.
My two 1g Honda Insights both called for 0-20, both had over 300k miles, and both got revd to redline. I also use thicker oil to boost oil pressure in loose engines. To me what oil i run depends almost totally on what hot idle oil pressure i see on whatever claptrap i happen to be maintaining.
Something else to keep in mind is fuel dilution. Iirc Mazda switched the 2.0 in the nc to gdi (has direct injection). Because of that you will see mire fuel in the oil than a normal mpi engine. Many manufacturers expect 4-7% fuel in the oil as normal as long as there is not increased wear or drop in viscosity. Many 0w oils have so many vis improvers that they are inherently better at managing fuel than the older oils, and certai synthetics better still.
so keep in mind there are a lot of things going on in there over just protecting bearings. Oil is pretty awesome in all the different things it does in an engine and the technology behind it is pretty intense.
honestly, and I'm not selling myself here, the best way to get your answers is to test it. Run an oci with the correct oil and test and one with the 20 and test. Do you see more wear between the two? How are the ciscisitirs holding up? Is the oxidation increasing differently indication the oil is overheating etc. we can ask questions online and get 100 different answers. But the only way to find out what will work for YOU is to test and see
In reply to bobzilla :
The NCs were all port injection. DI didn't get adapted until the ND with the Skyactiv motors.
In reply to flatlander937 :
Do the NCs have variable valve timing, though?
If they do, and it's fully variable and not just advanced/retarded, you really want to use the grade of oil specified because the solenoid actuation was calibrated for that.
Step 1 in any VVT diagnosis is "Is the oil full and of the correct viscosity?"
In reply to Knurled. :
They do. It's remarkably similar to NB VVT. Variable up to +/- 40 degrees IIRC.
They are a lot more tolerant of oil weights than you think. As are nearly all cars.
A 0w20 and a 5w20 oil are roughly the same viscosity at 40F. I believe it is the Pennzoil Platinum 0w20 that is actually THICKER than 5w20 at normal 60-70F temps.
Oils that are 0w weighted are rated as such at different temps than 5w.
https://www.bobistheoilguy.com/putting-the-simple-back-into-viscosity/
Also, 0w at normal ambient temperatures is still considerably thicker than even an AnythingW30 oil at 212F. It's not like the VVT bits are tolerant for certain weights at certain temperatures. It changes from dozens to 100+ cSt viscosity to <10cSt or so depending on oil in question.
I've run 0w20, 10w30, 5w30, 0w30, and 0w40 all in my Mazda2. All have been run on track
The B Spec guys run 0w20. They do not have problems with blowing up engines. They do call for 0w20 in the US, but everywhere else 5w30 to 10w40 is recommended.
I have 166k on my car. The VVT function on my 1.5l is identical to the 2.0/2.3/2.5l Duratec/MZR such as what is in the NCs.
Most service manuals dictating to check oil viscosity are just trying to avoid warranty claims and/or keep as many unknown variables as possible when there is a problem.
Obviously you want good oil when beating on your car, but for the vast majority of people, as long as there is something API rated in there, and they do regular changes, everything will be just fine.
In reply to flatlander937 :
Speaking here of the service side of the industry. Yeah, most cars nowadays are more tolerant but the early stuff wasn't always tolerant of, say, someone dumping 10W30 in where 5W20 was specified.
The real subtext of that statement in the trouble tree is "What do you think is the viscosity of 9,000 mile old oil that reeks of gasoline?" Answer: Change the oil before you go any further, oh and use the viscosity we specify kthx.
flatlander937 said:In reply to bobzilla :
The NCs were all port injection. DI didn't get adapted until the ND with the Skyactiv motors.
Ahhhh... I know some of those went in 2008 but not in what chassis.
In reply to Knurled. :
Of course. I work on all makes and models and can honestly not recall a single car that had a failure due to wrong oil in 15yrs.
Wrong or defective filter? Yes. Diluted oil/low level/too long since last interval? Yep.
I just wanted to clarify that changing from 5w30 to 0w20 will likely never cause problems in and of itself.
The best solution is to monitor oil temp and pressures and adjust as necessary.
I stand by 0w-whatever oil being superior to anything else for daily or even autocross type stuff (all else equal, and it never is).
Less viscosity difference from the winter rating to normal operating temp means less additives or modifiers or whatever are needed, and the oil will break down/lose viscosity slower... Which is why most racing oils are not 0w and or just a straight 30/40/50wt.
In reply to flatlander937 :
I run 0W30 in my Volvo that specifies 5W30, and it has CVVT on both camshafts. I strongly believe in 0W oils too, I like the cold flow.
I have seen the wrong oil cause VVT issues before, on a 3-valve Ford. Some lube jockey used 5W30 and the engine didn't like it. Drained it out and put in 5W20 and it was fine. I guess it was the one Ford made that year that had tight bearing tolerances.
My take on specs is, I'm not the engineer. If they care enough to give me a spec, I'll care enough to use that spec. (I'll experiment with my OWN cars, but I can easily assume the responsibility if I cause an issue. Not going to play with paying clients' cars like that)
You'll need to log in to post.
