Switching from 5w-20 to 15w40 for Mazda MX-5

[KL2BE]

My 2006 Mazda MX-5 roadster calls for 5w-20.
That goes against my old fashioned sensibility; being a motor-head from the '60s and being concerned that my Sprinter RV (diesel), Yamaha 920 HR motorcycle and roadster all outlive me. I am skeptical of the 5w-20 recommendation; suspect it was all about MPG ratings and not engine longevity.
I am inclined to use Delo 400 15w40 or Mobil Delvac 1300 15w40 in the Mazda as I do in the Sprinter and the Yamaha 920 HR.
Is there a down-side to using the heavier Delo or Delvac?
The Mazda has a highly tuned engine (getting 170-hp from 2.0 liters) but I change oil every 3,000 miles (not because it is used up but because that's my annual mileage).

 

[sunfire]

Delo and Delvac might be too thick for Alaskan weather. Which causes even more wear during startup and warmup stages.

 

[Max_Wander]

10w30!

 

[Drew99GT]

Originally Posted By: KL2BE

Is there a down-side to using the heavier Delo or Delvac?


Yup. The motor will likely feel less peppy/rev happy, fuel economy will drop, and you could cavitate the oil pump on a nice 20 below Alaskan winter start.

5w-20 has proven to be an exceptional oil grade - better fuel economy, easier cold starting and cold weather engine protection, and excellent wear control. There's been no proven increase in wear from using the new thin oils - if anything, based on several UOA posted here from 5w-20 used in vehicles NOT SPECED FOR IT, 5w-20 has shwon a decrease in wear.

 

[d00df00d]

In the old days, oils had to be thick to protect well. That is because they relied almost exclusively on hydrodynamic lubrication, i.e. the oil had to be moving to work.

Modern oils are different because they are much better at barrier lubrication: they create highly durable and very slippery films on metal surfaces that provide all the protection you need. That's why your Mazda can have 85 hp/L and still use a 5w-20.

You probably can run a 15w40 in your MX-5, but you will be making two big sacrifices. First, a 15w40 will not flow as well in your MX-5's narrow oil passages on a cold start. So, every time you start it up, some parts of your engine will spend several seconds (maybe even up to a minute) without much oil. That can be murder in winter: a conventional 15w40 will turn to molasses in freezing temperatures, and will hardly pump at all in a system designed for a 20-weight oil. Second, since the it will take a lot more force to push that thick oil through the engine, you will lose power, response, and fuel economy.

My advice is to stay in spec. It may be hard to break old habits, but remember that the MX-5 is a well designed car; if Mazda calls for a 5w-20, there's a good reason for it.

 

[sunfire]

Originally Posted By: Drew99GT
Originally Posted By: KL2BE

Is there a down-side to using the heavier Delo or Delvac?


Yup. The motor will likely feel less peppy/rev happy, fuel economy will drop, and you could cavitate the oil pump on a nice 20 below Alaskan winter start.

5w-20 has proven to be an exceptional oil grade - better fuel economy, easier cold starting and cold weather engine protection, and excellent wear control. There's been no proven increase in wear from using the new thin oils - if anything, based on several UOA posted here from 5w-20 used in vehicles NOT SPECED FOR IT, 5w-20 has shwon a decrease in wear.


I agree with everything you said. Went to 5W-20 from 10w30 and the engine feel more peppy.

 

[KL2BE]

Originally Posted By: sunfire
Delo and Delvac might be too thick for Alaskan weather. Which causes even more wear during startup and warmup stages.

The Mazda roadster is ONLY driven with the TOP DOWN. Meaning over 65F!
Why do you think I only drive it 3,000 miles a year?

 

[Yuk]

Originally Posted By: KL2BE
Originally Posted By: sunfire
Delo and Delvac might be too thick for Alaskan weather. Which causes even more wear during startup and warmup stages.

The Mazda roadster is ONLY driven with the TOP DOWN. Meaning over 65F!
Why do you think I only drive it 3,000 miles a year?


Regardless... I think you're missing most of the excellent points. Your experience served you well for most of you're car-owning life, but it's now time to get with the times. Even if you lived in California or Texas, it would still be in the MX-5's best interest to run 5W-20, not 15w40. The only time I think most knowledgeable BITOGers would say differently, is if the car were to see a lot of high temperature abuse... Like heavy track time.

 

[ericthepig]

In case you still want that xxw40 - chk out M1 0w40 - excellent cold cranking visc, but then at Op temp you'll have your 40 grade.

 

[Drew2000]

If you want to go a bit thicker, why not use 5w30? In my 5w20-spec Duratec Tribute, I'm currently running 5w30 Valvoline Synpower (got on sale) and the engine loves it. I have no problem running 5w20/0w20 though and that will be in my engine for winter.

If you just have to use HDEO, try a 5w40 like Rotella. Better start-up flow than the 15w.

Drew

 

[JohnBrowning]

It is not going to hurt it in any way other then it will but some drag on the engine but that is about it. Seeing how it see's such little driveing why not use a 5W40.In fact all of your vechiles that you currently use a 15W40 on would like a 5W40 just as much and it is a more flexable oil for your cold environment if you should ever want to start them int he winter. Their is not a engine in any car or truck sold in the USA that is going to self destruct because someone put 15W40 in it!

 

[coffee]

I agree with using a 5w40 oil.

 

[oily boyd]

I had a '90 Miata and I used 5w30 all her life.

Yours is a lot newer, I haven't kept up with all the changes but 5w30 is slightly thicker (what you're looking for) and a lot of good choices if you your a "sale" shopper.

I'd like to get another someday... is the oil filter still accessible from top of engine?


That thing will run forever on any of the viscosities discussed so far.

Have fun!

 

[Cutehumor]

wow, those miatas are great roadsters. I talked to my wife about buying one the other day. she wouldn't even budge. I should show her this thread, even a guy in Alaska has one! However, I agree, use 5w-20 with confidence

 

[BuickGN]

Originally Posted By: d00df00d
In the old days, oils had to be thick to protect well. That is because they relied almost exclusively on hydrodynamic lubrication, i.e. the oil had to be moving to work.

Modern oils are different because they are much better at barrier lubrication: they create highly durable and very slippery films on metal surfaces that provide all the protection you need. That's why your Mazda can have 85 hp/L and still use a 5w-20.

You probably can run a 15w40 in your MX-5, but you will be making two big sacrifices. First, a 15w40 will not flow as well in your MX-5's narrow oil passages on a cold start. So, every time you start it up, some parts of your engine will spend several seconds (maybe even up to a minute) without much oil. That can be murder in winter: a conventional 15w40 will turn to molasses in freezing temperatures, and will hardly pump at all in a system designed for a 20-weight oil. Second, since the it will take a lot more force to push that thick oil through the engine, you will lose power, response, and fuel economy.

My advice is to stay in spec. It may be hard to break old habits, but remember that the MX-5 is a well designed car; if Mazda calls for a 5w-20, there's a good reason for it.


There are no parts of the motor that will come even close to a minute without oil. I would bet oil gets everywhere it needs to go within about 2 seconds. I've forgotten to install the 5/16" turbo feed line to the turbo which is at the top of my motor with a 15-50 oil on a cold day and in less than a second I had a windshield covered in oil. Most overhead cam cars are designed where the lobes of the cams will dip into little puddles of oil so super quick pressure up there isn't really needed.

 

[Ken42]

Don't forget if you have those fancy valve timing changing things they do require oil to run and the thinner the better.
My elantra an 05 specs 5W-20 cause of this and its tiny oil passages. And fuel economy can not forget that. Have also been told they use a low pressure pump to save fuel and pump up the pressure with the smaller oil lines.
Your choice run what ever you want but if it blows and is under warranty do not expect much help from Mazda.

Ken

 

[KA426]

Mobil 1 0w30 or 0w-40. That way you'll have your cold start protection plus higher temperature protection. Best of both worlds.

 

[csandste]

I'm running ST 5w20 in 100 degree temperatures in Missouri in my 07 Optima with absolutely no issues. 15w40 in cold weather sounds like murder on an engine like that. It's not the sixties.

 

[d00df00d]

Originally Posted By: KA426
Mobil 1 0w30 or 0w-40. That way you'll have your cold start protection plus higher temperature protection. Best of both worlds.

Aren't those oils still thicker at most temperatures than most 5w-20s?

On a warm day, you would definitely still get better cold start lubrication from a good 5w-20 than you would from Mobil 1 0w-40...

 

[drivewaytech]

Stated it before. I dropped 5 qrts. of 5w30 Synpower in my 5W-20 spec'd car and developed an intermittent lifter tick on an engine with under 60K miles. Perhaps it was just complete coincidence, but it made me take heed of manufacture’s specifications. Even in the hot climate of Georgia, I will stick to 5W-20.