0w20 or 5w20

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Ottawa, Ontario
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17 Mazda 6 GT
If you're still under warranty you should follow Mazda's recommendations.
When I went to 0w30 last year, it was done at the dealership and I asked about warranty. They said no problem.

Since my last post, I did an oil change this spring and went back to 0w20. I'm noticing now with the current warm weather we are having that the engine is noisier again. I checked my oil level and it looks dirty, even though I haven't driven much.
It's not scientific I know, but my gut experience is telling me that 0w20 in the current heat we are having is too thin. I also suspect it's more prone to dilution (gas in oil) under these conditions.
I'm definitely changing to 5w30 in the next week or two.
 

madar

Contributor
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2016.5 CX 5 Touring AWD, 2015 SCION XB
No doubt 0w-20 is panther piss oil. But different brands give you different results. I'm switched from Pennzoil PP to Castrol Magnatec 0w-20 in my Scion, difference is night and day...way quieter. I'm running a full synthetic PAO 0w-20 oil in my CX5, virtually no noise at all, oil consumption is way down , gas mileage is up. I don't know how car companies are even specifying 0w-16. That stuff must really be watery.
 

ColoradoDriver

Gen-1 Kodo Design
Contributor
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Denver, CO
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2014 CX-5 Touring
I've been much happier running 5w30. Less oil loss/consumption between changes was the biggest thing I noticed. I should really get around to another oil analysis, I've yet to send one in with the 5w30.
 
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Mazda CX 5 Touring
The thicker the oil the more it lubricates that's a fact. The thinner oil is recommended primarily to save gas. Going up a little in weight doesn't hurt just don't go as far as 90 weight gear oil. You could run straight 30 weight oil and it wouldn't hurt. In Florida I run 5 or 10w20 in the summer and in winter I run 0 or 5w20. I could run 5w20 all year long with no detrimental results.
 
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Ottawa, Ontario
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17 Mazda 6 GT
The thicker the oil the more it lubricates that's a fact. The thinner oil is recommended primarily to save gas. Going up a little in weight doesn't hurt just don't go as far as 90 weight gear oil. You could run straight 30 weight oil and it wouldn't hurt. In Florida I run 5 or 10w20 in the summer and in winter I run 0 or 5w20. I could run 5w20 all year long with no detrimental results.
10w20, 5w20, 0w20 shouldn't make a difference in warm/hot weather. The second number (20) is the key consideration for hot environments. The first number is something to consider in cold/winter climates.
Personally, I'd run a 30 weight oil in a warm southern climate. I'm definitely switching back from 0w20 to a 30 weight oil in the very near future.

BTW, a blanket statement like the thicker the oil, the more it lubricates, is a bit of a reckless statement.
Today's engine tolerances are much tighter than in the past. At some point in the process, a thicker oil will actually lubricate less because the oil pump cannot pump with enough pressure to get the oil into the tight spaces between the rod bearings and crank journals, as well as the cam shaft bearings. The oil is simply too thick to be effectively pumped into those tight spaces, resulting in lower oil pressures and less lubrication. Thicker oil will also increase engine heat, as the engine and pump have to work harder to overcome poorer oil flow. There's a reason why newer engines don't recommend 20w50 oils anymore.