'93 miata 10w-30 or 5w30?

[k24a4]

Does it really matter?

I drive it from early Spring to late Fall here in the Northeast putting anywhere from 3000-5000 miles on it. Fresh oil, usually an inexpensive dino, is poured in before it is stored for the Winter, then, in the Spring, changed out for synthetic after a few hundred miles.

So it sees some colder cold starts in the Spring and Fall, and during the Summer, of course, will run in higher temps, 80 degrees and up.

I don't drive it hard, but the little 1.6 liter will rev at approximately 4000-4500 on the highway going 70-75 mph.

The manual really is not much of a help as 5w-30 and 10w-30 are both specified for the ambient temperatures I drive in, and preference is given to neither. It puzzles me why they would even make the distinction, since the 5w-30, according to the chart, is good from below -20 to over 100 degrees F, while the 10w-30 is good from 0 to over 100 degrees F. Why not just specify 5w-30 and be done with it?

I know the cold starts are helped by the 5w, I guess my question is whether the 5w-30 offers adequate protection when I am running it during the Summer in the higher temperatures.

 

[dparm]

There's really no reason not to get 5w30 in there.

5w30 and 10w30 perform identically at higher temps since they both become 30 weights.

 

[webfors]

Because 10w30 is more shear resistant, and therefore more 'ideal' in hot temps. If you don't drive it in the winter put 10w30 in and don't look back. T5 might be a good choice for that older engine.

 

[dparm]

AFAIK the Miata motors aren't terribly hard on oil so I wouldn't worry too much about shear stability.

 

[MegaCorp]

Changing the Dino after a few hundred miles seems like a waste. Why not leave in the synthetic all year? It can handle that little use and not break a sweat.

 

[ARCOgraphite]

Originally Posted By: dparm
There's really no reason not to get 5w30 in there.

5w30 and 10w30 perform identically at higher temps since they both become 30 weights.
Dparmesan, You should make that assumption. Also We should not generalize but compare specific oils. a Proper 10w should be more shear stable and have a higher HTHS and a lower NOACK %OFF. Does sub-zero cold flow matter here? NO. Will he see any diff betwixt the two? Depends on the brand choice.

 

[k24a4]

Originally Posted By: MegaCorp
Changing the Dino after a few hundred miles seems like a waste. Why not leave in the synthetic all year? It can handle that little use and not break a sweat.


Well, the dino is sitting in the sump during storage from about November through March, or five months. I like to get the old used oil out in favor of the new for storage purposes. The idea of oil fairly saturated with contaminants, including acid, from use starting in April and ending in November sitting in the sump during storage does not appeal to me. I know it may seem like a waste but I want to do what is best for the car since I plan on holding onto it indefinitely.

 

[k24a4]

Originally Posted By: ARCOgraphite
Originally Posted By: dparm
There's really no reason not to get 5w30 in there.

5w30 and 10w30 perform identically at higher temps since they both become 30 weights.
Dparmesan, You should make that assumption. Also We should not generalize but compare specific oils. a Proper 10w should be more shear stable and have a higher HTHS and a lower NOACK %OFF. Does sub-zero cold flow matter here? NO. Will he see any diff betwixt the two? Depends on the brand choice.


I've had the car since the Spring of '07. It has only seen Mobil 1 5w-30 or 10w-30 since that time. However, this year I plan on going with Kendall liquid titanium, a blend, for the Summer because I got a good deal on it, $1.99/ qt. I'm also thinking of going with PYB or Platinum, which I use in the Honda, going forward. I still have 6 qts of Mobil 1 10w-30 left over. Not sure when I will use it.

 

[Stan]

GC 0W30 works great in Miatas…and often quiets them down a bit (subjectively).

 

[wander2039]

Originally Posted By: k24a4

I don't drive it hard, but the little 1.6 liter will rev at approximately 4000-4500 on the highway going 70-75 mph.


It revs that high? Is it missing a gear? Even my 3spd Festiva with the 1.3 (think of it as the 1.6's little brother) runs 3500 rpm at 70. I think the Mazda's of this design prefers 10w30 gas mileage and overall run-ability. Anything lower than 5w30 your gas mileage will drop. 10w40 and above it's a bit smoother but gas mileage drops a small amount.. probably to small to notice most of the time. Really you can run just about any weight but 5w20.

 

[Audi Junkie]

I would use 10w-30 until cold dictated otherwise.

 

[mechtech2]

I'd use 5-30.
Shearing problems at 3K? Gimme a break.

 

[Bluestream]

Originally Posted By: k24a4
Originally Posted By: MegaCorp
Changing the Dino after a few hundred miles seems like a waste. Why not leave in the synthetic all year? It can handle that little use and not break a sweat.


Well, the dino is sitting in the sump during storage from about November through March, or five months. I like to get the old used oil out in favor of the new for storage purposes. The idea of oil fairly saturated with contaminants, including acid, from use starting in April and ending in November sitting in the sump during storage does not appeal to me. I know it may seem like a waste but I want to do what is best for the car since I plan on holding onto it indefinitely.


In that case, change oil in the fall, and have your new oil sit there and be ready for spring. It wont go bad sitting in the sump. No need to double change it.

 

[milehigh]

I run T6 5w40 in my '90 Miata with no issues.

 

[Audi Junkie]

Originally Posted By: Bluestream
Change oil in the fall, and have your new oil sit there and be ready for spring. It wont go bad sitting in the sump. No need to double change it.


+1

 

[k24a4]

Originally Posted By: Bluestream
Originally Posted By: k24a4
Originally Posted By: MegaCorp
Changing the Dino after a few hundred miles seems like a waste. Why not leave in the synthetic all year? It can handle that little use and not break a sweat.


Well, the dino is sitting in the sump during storage from about November through March, or five months. I like to get the old used oil out in favor of the new for storage purposes. The idea of oil fairly saturated with contaminants, including acid, from use starting in April and ending in November sitting in the sump during storage does not appeal to me. I know it may seem like a waste but I want to do what is best for the car since I plan on holding onto it indefinitely.


In that case, change oil in the fall, and have your new oil sit there and be ready for spring. It wont go bad sitting in the sump. No need to double change it.


I did exactly that this year. I kept the pyb 5W-30 that I exchanged last Fall for storage in the car for the Summer '11 run with a can LM Mos2 added in April to boot. I'll get a UOA on it when I swap it out in November.

Thanks for the advice. BTW I sent my first ever oil sample to Blackstone recently. It was pyb sm 5W-20 plus 1 can lm mos2 with ~6100 miles on it from the Honda 2.4. I'll post the results when I get them.

Thanks again.

 

[Cujet]

My 94 Miata started showing excessive wear when I put 0W-20 in it, as an attempt at more HP and free-er revving stock engine. 250PPM Pb!

When I used Mobil 1 15W-50 and a turbo at 24 pounds boost I saw 5PPM Pb. So, there was no question the Miata engine did well with the heavier oil.

Interestingly enough, the oil pressure was horrible with the thin oils. The Miata oil pump has very limited capacity, and the bearings are not particularly tight. 0W-20 M1 resulted in a maximum cold oil pressure of 50 PSI and a maximum hot oil pressure of 30PSI at 5000 RPM. Not exactly great numbers.