Is recomended oil grade 5-20 a MUST?

Zorba

Member
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Mazda CX 9 GT
I did internet research on that issue and find out that MAZDA has to justify their mileage data on the sticker by recommending thin oil.

Sure, it might not damage the engine during the warranty period. I believe that during hot summer months the wear and tear will be excessive on 5-20.

I plan to keep this car for longer than 5 years and want somebody to convince me that 5-20 will be better than 10-30 for the summer.
 
Our home temps run from single digits to triple digits. Plus, we regularly drive in Phoenix and other 115+ locations. Never had one problem with the factory recommended oil. Not on this car, or previous cars.

They recommend a specific weight for a reason, and they know a lot more about why a certain oil should be used than you guys. It's not to skew their mpg ratings, either. If it were that easy, every car maker would do it, and GM wouldn't cut huge holes in their interior support panels to boost MPG.

You're more likely to cause a problem by second guessing the manufacturer, without knowing exactly what the different weights actually mean.


You also need to be careful when relying on information you find on the internet. There are a lot more opinions than facts.
 
Read your manual most say you can use other grades of oil as well.

My wife's Subaru says 5w30 is recommended, but goes on to say you can pretty much use any grade above 5w30 (not below, IE 5w20 etc) depending on your area/driving conditions, etc.

This is just for warranty purposes though. There is no way 5w30 or 10w30 is going to cause you engine problems if you were to use it.

5w20 was invented for CAFE purposes, nothing else.
 
From the manual:

"Use SAE 5W-20 engine oil"

There are no alternative weights. Temp range from -20 to 120+ is all 5W-20

There just isn't any justification to use a different oil. IF you did go heavier, and weight can affect MPG, you'd just be reducing it.
 
I, usually, do not blindly follow all the recommendations from the authorities.
Trying to think why do they recommend 5-20. Is it true that heavier oil will block some micro passages in the engine, or affect VVT?

Me personally, I am not much concern about the fuel economy as much as preserving the engine for the long time. I know that this is a gas guzzler, and there is not much we can do about it. What about you guys?

If you post a statement try to explain the reasoning. Strict orders can be utilized in the Patriot Act approach. We are trying to discuss stuff and find a some kind of solutions here. Is that right SportOwner?

By the way, I believe in Evolution and I'm not very "Religulous".
 
From past experience, the wrong oil in a HLA engine can gum up the lifters. I don't know what hydraulics the CX9 specifically uses, but 2 of my 4 Mazda trucks had permanent lifter problems after someone used the wrong oil.(One a previous owner, one an oil change shop) I do know that the CX9 has a complex valve system. I won't mess with it.

I trust Mazda to know exactly which oil should be used in the engine they built.
 

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You shouldn't have any problems with a quality 5w-20 and a good filter. The main reason that manfs. recommend the use of 5w-20 today is to meet CAFE stds for emissions and MPGs. There is a limit on the viscosity you can use. I wouldn't use a 50w oil as it would not circulate fast enough thru the oil passages, but a 30w is fine. In my speed 3, i run a 0w-40 for winter and 5w-40 for summer as opposed to the manf's recommendation of 5w-30.
 
OK. This is an expensive car - for me. The issue I'd like to discuss here is: Does MAZDA wants to cover it's a.. from the inspectors that are going to be checking the indicated mileage on their published sticker, and cares for the engine performing good - just for 5 to 6 years, OR they are absolutely sure that 5-20 oil will not damage the engine on 120 F for the 15 to 20 years.

I believe that winter driving will be fine on 5-20...but I am skeptical to have that oil in summer.

As a guy in late 40-s I believe to 10-30 for the summer. I know some guys that damaged their engines with thin oil - though, they were US made vehicles.
 
Just remember, a 10w30 oil at operating temp is still a 30w oil. Having assembled/torn down a few modern engines, I can tell you that 10w-30 is just fine. As oil degrades, the viscosity tends to get lower. Even a 30w can end up being a 20w over time. Bottom line, use a quality synthetic whether it's a 20w or 30w and you will be fine.
 
I've been using Mobil 1 0W-30 quite happily since my 1st oil change. I'm now on a 10,000 mile oil change interval. Oil analysis says I have a very happy engine. Just passed 50,000 miles.

I think 20 weight oils are just to thin and are a fuel economy gimmick for EPA ratings. If they used 20 weight oil for the EPA mileage tests then the manual HAS to tell you to use it. Most every engines runs fine on 30 weight oil.
 
Thanks guys! We are getting some agreements here.

It gets to 100 F, where I live here in southwestern Ontario. I also plan to drive in Florida this Summer; so that's where the concern is coming from.

As I see, most of you agree that synthetic 10-30 would be a good choice for the summer.

But...I remember the Dealer telling me to go with semi synthetic, since they did not test this engine with synthetic - for the reasons I can't comprehend.

Any clue regarding that issue?
 
Thanks guys! We are getting some agreements here.

It gets to 100 F, where I live here in southwestern Ontario. I also plan to drive in Florida this Summer; so that's where the concern is coming from.

As I see, most of you agree that synthetic 10-30 would be a good choice for the summer.

But...I remember the Dealer telling me to go with semi synthetic, since they did not test this engine with synthetic - for the reasons I can't comprehend.

Any clue regarding that issue?

The dealer is full of crap. No engine needs to be 'tested' with synthetic oil. Synthetic oil has been proven for 40 years now, it's not some recent development. I would not use 10W-30, use 5W-30 or 0W-30, they are all the same viscosity at operating temperature, but the 5W and 0W provide much better lubrication at startup and eliminate the need to think about seasonal oil changes. 10W-30 oil is a stopgap measure for older cars that leak/burn oil.
 
The recommended 5W-20 hasn't failed me driving in 115+ temps. Phoenix is hotter at 3am than most places are mid afternoon. Ick Home is 90 to low 100's all summer.
 
Just remember, a 10w30 oil at operating temp is still a 30w oil. Having assembled/torn down a few modern engines, I can tell you that 10w-30 is just fine. As oil degrades, the viscosity tends to get lower. Even a 30w can end up being a 20w over time. Bottom line, use a quality synthetic whether it's a 20w or 30w and you will be fine.

I've been using Mobil 1 0W-30 quite happily since my 1st oil change. I'm now on a 10,000 mile oil change interval. Oil analysis says I have a very happy engine. Just passed 50,000 miles.

I think 20 weight oils are just to thin and are a fuel economy gimmick for EPA ratings. If they used 20 weight oil for the EPA mileage tests then the manual HAS to tell you to use it. Most every engines runs fine on 30 weight oil.

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