NB Miata what oil?

I was at my local "do it for me" oil change shop a few weeks ago. It was time to put the Miata NB away for winter. I asked for 0w20 which was the lightest weight oil they have. That way after hibernation it will flow quickly upon startup. I drove it home, and fogged it with storage oil until it stalled at final shutdown.

"The do it for me" oil change guy said the 0w20 oil was far too light, and I should only start the car come spring, but not drive it to the shop as that would be to light an oil rather have it towed.

I called shenanigans on his advice especially the towing part immediately. Especially since I have found numerous accounts of others using the same viscosity with -apparently- no ill effects.

However, In the owners manual there is no recommended viscosity it just gives me a extremely vague chart with temperatures and viscosity listed

Question it this, what viscosity is best for a mostly street driven NB Miata? 1999, 5 speed, variable length intake.

10w30. Nothing fancy needed for the lump of iron BP engine.

I think I have Rotella in mine right now.

But really, for what you are doing, dont overthink it. 0w20 will be fine for spring startup and driving to the shop on a 50 degree day. I wouldn't trust it at 100 degrees and wfo though.

I'm not a Mazda guy, but 0W20 seems a tad light to me. OK, maybe, for super winter driving, like mostly sub freezing to "ZOMG IT'S BERKELEYING COLD, WHY THE BERKELEY DID I MOVE TO NEBRASKA?" If you were going to put it up for the winter, I wouldn't worry about it at all, just use whatever regular oil, like 5W30 synthetic. If the 0 weight is in there now, I wouldn't worry about driving it to a oil change place come spring. Don't think I'd go racin' with it, though.

You're overthinking this. 5W30 until the lifters start making noise and then go heavier.

2016 CX 5 Mazda oil spec is 0-20 synthetic. Didn't know I was supposed to tow it around.

Dumb question, why not run what Mazda says to run?

This engine is fairly old, so it's not designed for the more modern light weight oils.

The Skyactiv engine in the 2016 is very different from the BP in an NB.

I'm curious why the oil change guy thought it was OK to drive it home with 0w20 but not to drive it back to the store in March or so?

I think it's fine, just don't take it to Laguna Seca like that. :)

drsmooth wrote: I was at my local "do it for me" oil change shop a few weeks ago. It was time to put the Miata NB away for winter. I asked for 0w20 which was the lightest weight oil they have. That way after hibernation it will flow quickly upon startup. I drove it home, and fogged it with storage oil until it stalled at final shutdown. "The do it for me" oil change guy said the 0w20 oil was far too light, and I should only start the car come spring, but not drive it to the shop as that would be to light an oil rather have it towed. I called shenanigans on his advice especially the towing part immediately. Especially since I have found numerous accounts of others using the same viscosity with -apparently- no ill effects.

Yes, it's utter BS. If you have enough oil pressure at hot idle to not turn the light on, and the lifters stay quiet, the oil's thick enough.

Back inna day I used to run 5W20 in my rotaries instead of the 20W50 that everyone said you had to run. Bearing issues = zero. Same for my Volkswagen, I fed it 5W20 when everyone said the lifters would collapse if you didn't run 20W50 in them.

0W20 is thinner when COLD than 5W20, should be the same when hot.

(I won't get into all the times I've run ATF, which is 5W20 with a completely different additive package, as motor oil, even in a fairly well stressed turbo engine. Guess how many problems I had... go on, guess...)

Newer cars run 0W-20 to try and boost fuel economy numbers, tolerances are also much tighter and they will have had synthetic since new. It's not that you CAN'T run that in a Miata but it strikes me as too light on the hot viscosity for an older sports car engine, at least for any kind of spirited driving.

In my old Miata the lifters made a ton of noise with anything less than 5W-40. Rotella was always my oil of choice.

Maybe I am weird but I don't understand having changed the oil for storage of a car, especially something like an MX-5. Maybe change it before storage and then run it all next driving "season".

In reply to pres589:

That is what I understood the idea was. Get the old, acidy oil out of the engine and new oil in the engine, then it should be good to go next season.

In reply to Knurled:

Maybe it was and some replies confused me.

The "confusing" chart in the owners manual basically says 10W30 works for all temps and 5W30 is for cold temps. I use 10W30 in just about any B6 or BP engine. 10W40 for track use on tired engines.

The light (aka the pseudo gauge) triggers at about 7 psi. I wouldn't use it as a guide for good enough, personally.

Rotella T6 to quiet down the miata tick.

In reply to Keith Tanner:

The bearings get supported by forces completely independent of pressure. We feed the bearings oil under pressure for cooling reasons. Given that the oil pump is a positive displacement device, I don't see 7psi being a real problem as long as the lifters are happy. If anything, 0W20 probably flows more actual oil through the engine despite lower gauge pressure because the oil would cavitate less on its way to the pump, increasing volume flow out of the pump. (I am assuming here that the oil is a froth of air bubbles)

Another way, we use oil pressure as a somewhat poor indicator of volume flow from the pump. If the bearing clearances are the same, and the oil pump volume is the same, but oil pressure is lower with lower viscosity oil, that just means the oil pump is dragging less on the engine, and you get more power at the crank and better fuel economy.

In reply to Keith Tanner:

10w30 is more shear stable than 5w30, this probably mattered in the 90s and they were concerned about shearing the oil too thin for summer use. A modern 5w30 should be fine year round, especially a full synthetic oil.

You guys do what you want 10W30 and good oil pressure has been keeping BPs happy for a quarter century, I have no reason to change.

So after the break, I need to visit a tribologist at work. Gain some insight to this.

alfadriver wrote: Dumb question, why not run what Mazda says to run? This engine is fairly old, so it's not designed for the more modern light weight oils.

OP drsmooth said: However, In the owners manual there is no recommended viscosity it just gives me a extremely vague chart with temperatures and viscosity listed

codrus wrote: I'm curious why the oil change guy thought it was OK to drive it home with 0w20 but not to drive it back to the store in March or so? I think it's fine, just don't take it to Laguna Seca like that. :)

I thought the same which is why I called shenanigans. The only logical reason I can think of is the shop guy gets 2 oil changes for the price of one.

Keith Tanner wrote: You guys do what you want 10W30 and good oil pressure has been keeping BPs happy for a quarter century, I have no reason to change.

The "confusing" chart in the owners manual basically says 10W30 works for all temps and 5W30 is for cold temps. I use 10W30 in just about any B6 or BP engine. 10W40 for track use on tired engines.

If this makes a difference it is the Canadian owners manual. I have been told there is a difference between owners manuals in the U.S. and Canada, according to what I have been told the U.S. manual is specific as to the oil to be used in specific temp ranges, where as the CDN manual has a horizontal line graph showing a bunch of grades and a bunch of temps.

Seeing as how he has forgotten 10 times what I will ever know about the Miata/Eunos/MX5 probably the Fiat 124 too.

I'm going to go with Kieth Tanner's recommendation. Although a followup question for him.

The "do it for me" oil change place said to not drive it at all with 0w20 oil, just to start it I'm assuming they are full of "S".

I'm actually more familiar with the Canadian manual - I know exactly what the chart looks like I've got my original Canadian 1990 parked in my garage right now.

I agree with the previous opinions, the car should be fully driveable with 0w20 but I wouldn't stress it too hard.

I have only had my NB for a couple of months, so I am new to the Miata game. I also live in Texas, so my cold weather opinion is not well-formed by experience. But... I do have an uncle who is a petroleum engineer and drag race enthusiast, and I do own a Mazda RX-8 track car, which is absolutely brutal on motor oil.

My uncle's informed opinion is to use the thinnest oil that will maintain adequate pressure in every situation, and keep the cold and hot viscosity numbers as close as possible to prevent breakdown of the viscosity improvers. He builds his own engines for his Camaro drag car and is obsessive about taking wear measurements. He says there is no statistical significance between wear in lower viscosity oils (20-30W), but heavier weight oils, such as 20W50 show more measurable wear, even in warmer climates. When asked about 40W oil, he expressed little opinion beyond "use it in engines that need it". I assume he has little data on 40W. His personal choice in viscosity for his Camaro is 10W30.

So, of course, I ignore all of his advice and use 0W40 in my RX-8. The US owner's manual calls for 5W20 conventional oil in all climates. In other countries, the manual shows the typical spread from 5W20 to 10W30 synthetic oil, depending on climate. According to several used oil analyses done for me by Blackstone Labs, 20W off-the-shelf synthetic oils shear down to 10W in a single track day. 30W oils typically fare a little better. The two oils I have found that can stand up to the Renesis rotary engine (not counting boutique oils like Amsoil, Redline, etc.) are Mobil 1 0W40 and Shell Rotella T6 5W40. Both of those oils can survive 3 track days plus driving 90 miles each way to and from the track without significant viscosity breakdown--shearing down to just under 30W under that abuse. I use Mobil 1, when I have the cat installed, and Shell when I don't, due to its lower price. Maybe this is just one of those engines that "needs" 40W. I digress.

My plan for my NB track car is to run a good quality 10W30 synthetic year-round and keep an eye on it. If I lived in the frigid North, I would probably run 5W30 in the winter and 10W30 in the summer and call it good.

I have no idea why the OP would receive the advice he did. If an oil is good to drive home from the shop before winter, it is good to drive back to the shop after winter. It doesn't go through much in terms of chemical change from sitting in the oil pan doing nothing for a couple of months. My only advice to the OP would be to start changing your own oil and stop paying oil change monkeys to be screw ups.

In reply to SteveDallas:

Excellent post and great information.

As far as changing it myself. Usually I do my own work provided the weather is good. In this case it was my first time storing a car (I just got this one,although I used to own a NA which I drove all winter), and it was too cold to change the oil in the driveway. once the temp drops below 40 my knees only agree with me farming things out