.png){kind=logo}
You’re only seeing the surface.
Our most active car forums and technical guides are reserved for registered users.
Sign up here to get total access and start sharing your own ride.
Our most active car forums and technical guides are reserved for registered users.
Sign up here to get total access and start sharing your own ride.
Yet another inquiry on the inline 6 turbo's oil weight
-
zafershoukat3109
- Posts: 57
- Joined: Mon Feb 02, 2026 8:46 pm
Viewing a handful of films on YouTube has led me to believe that 0w-20 may be more beneficial for gas mileage, while 5w-30 may be better for the turbo's health. Look at this video that a certified mechanic from Mazda in the US made. At roughly 29 minutes and 34 seconds into the video, there is a discussion about air weight. He used 5w-30.
-
zafershoukat3109
- Posts: 57
- Joined: Mon Feb 02, 2026 8:46 pm
-
davejacobs
- Posts: 37
- Joined: Mon Feb 02, 2026 8:34 pm
In my opinion, there's more going on with oil viscosity than just mpg. Here are a few important reasons why oils with lower viscosities are becoming more popular:
Modern engines are constructed with clearances between moving parts, such as bearings and pistons, that are microscopically thin. This results in tighter engine tolerances. In contrast to 0W oil, which circulates in an instant, thicker oils (such as 10W-30) are unable to flow adequately through these small openings.
Thinner oil produces far less internal drag and resistance, allowing for maximum fuel economy. Reduced energy use during oil pumping directly correlates to improved petrol mileage, an important metric for car manufacturers aiming to fulfil stringent federal CAFE (Corporate Average Fuel Economy) regulations.
Quick Start-Up Protection: The initial few seconds of starting the vehicle are the most critical for engine wear. When it's chilly outside, 0W oils can reach engine parts far more quickly than heavier lubricants can because of how rapidly they flow.
Oil that flows more freely allows the engine to reach its operating temperature more rapidly, which in turn reduces emissions. Greenhouse gas emissions are decreased as a result of this quick warm-up, which decreases incomplete combustion.
Oils with a 0W rating and a protective layer at high working temperatures (like 0W-20) are nearly always manufactured using full synthetics, thanks to advancements in synthetic chemistry. Chemically modified oils provide several advantages over their conventional counterparts, including increased stability and resistance to degradation in extremely hot environments.
Modern engines are constructed with clearances between moving parts, such as bearings and pistons, that are microscopically thin. This results in tighter engine tolerances. In contrast to 0W oil, which circulates in an instant, thicker oils (such as 10W-30) are unable to flow adequately through these small openings.
Thinner oil produces far less internal drag and resistance, allowing for maximum fuel economy. Reduced energy use during oil pumping directly correlates to improved petrol mileage, an important metric for car manufacturers aiming to fulfil stringent federal CAFE (Corporate Average Fuel Economy) regulations.
Quick Start-Up Protection: The initial few seconds of starting the vehicle are the most critical for engine wear. When it's chilly outside, 0W oils can reach engine parts far more quickly than heavier lubricants can because of how rapidly they flow.
Oil that flows more freely allows the engine to reach its operating temperature more rapidly, which in turn reduces emissions. Greenhouse gas emissions are decreased as a result of this quick warm-up, which decreases incomplete combustion.
Oils with a 0W rating and a protective layer at high working temperatures (like 0W-20) are nearly always manufactured using full synthetics, thanks to advancements in synthetic chemistry. Chemically modified oils provide several advantages over their conventional counterparts, including increased stability and resistance to degradation in extremely hot environments.
Although not entirely false, those bullet points do not address the question of why the same engine in different markets is specified with varying oil viscosities by the manufacturer. For the 3.3L engine in the CX-90, Mazda recommends 5w-30 outside North America and 0w-20 inside the US and Canada.
One variable is cold weather performance. Viscosity and temperature tables are provided in the CX-90 manual. The permissible range for 0w-20 extends approximately 10 degrees lower, beyond -30°. If it's not a regulatory issue, then what is the difference, aside from temperature?
On the whole, 0w-20 and 5w-30 oils aren't all that different in terms of how they work. I think either one will work just fine, particularly if you change the oil more frequently to keep it from shearing or diluting too much below its rated viscosity specification.
One variable is cold weather performance. Viscosity and temperature tables are provided in the CX-90 manual. The permissible range for 0w-20 extends approximately 10 degrees lower, beyond -30°. If it's not a regulatory issue, then what is the difference, aside from temperature?
On the whole, 0w-20 and 5w-30 oils aren't all that different in terms of how they work. I think either one will work just fine, particularly if you change the oil more frequently to keep it from shearing or diluting too much below its rated viscosity specification.
-
AndrewGuidon67
- Posts: 59
- Joined: Mon Feb 02, 2026 8:44 pm
It seems to me that the far tighter tolerances used to make new engines are a major contributing factor. Precision in computer-driven milling, boring, etc., has greatly improved over the years. Although it's only one small detail, I believe it to be crucial.
Although lubricant composition and tolerances certainly account for these engines' ability to run on thin oil, it remains unclear why Mazda specifies two distinct viscosities for the same engine in various areas. Tolerances for 3.3L Mazdas are the same worldwide as they are in the US and Canada, however, 0w-20 is recommended for use in those regions, while 5w-30 is recommended for the rest of the world.
Which one is "better"? There isn't always a clear winner in engineering. A great deal of uncertainty exists. Potential benefits and drawbacks must be considered. At normal temperatures and loads, I believe both viscosities are within the allowed range for this engine and application according to the Stribeck curve. It's safe to assume that 0w-20 is something Mazda is requesting in order to satisfy some regulatory requirements, likely concerning emissions or fuel efficiency in North America. Given that oil will gradually become diluted, polluted, and shear out of its stated viscosity with time, it is possible that Mazda specifies 5w-30 elsewhere to offer superior lubrication for longer periods between oil changes.
Considering my individual application... (1) Since 0w-20 provides better starter lubrication when cold, it will be useful to me as a resident of a region with very cold winters. (2) I usually replace the oil after approximately 5,000 miles, which is half of the recommended period by Mazda. Perhaps I am an exception to the rule that states most markets should use 5w-30, as I have a hunch that 0w-20 with 5,000 miles on the odometer will lubricate better than 5w-30 after 10,000.
Considering my individual application... (1) Since 0w-20 provides better starter lubrication when cold, it will be useful to me as a resident of a region with very cold winters. (2) I usually replace the oil after approximately 5,000 miles, which is half of the recommended period by Mazda. Perhaps I am an exception to the rule that states most markets should use 5w-30, as I have a hunch that 0w-20 with 5,000 miles on the odometer will lubricate better than 5w-30 after 10,000.
-
AndrewGuidon67
- Posts: 59
- Joined: Mon Feb 02, 2026 8:44 pm
As for my reverse flux magnetron discombobulator, I really like using the 0W-20. My cardiologist recommended it and mentioned that it would also help with my gastroventricular. "Something is seriously wrong" if a 0w-20 vs 5w-30 can ruin an engine, in my opinion. Similar to engine crohn's disease or diabetes