Ususally I change my own oil and use Mobil 1 5W-30 oil, but today I went to Mazda dealer to get oil changed and they use Mazda 5W-20, which the maintenance book recommends.. I have never used anything but 5W-30 or 10W30 in my gas engines, so what gives, why the change??

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2000 Ford 7.3 Powerstroke 4x4
2006 Mazda Tribute
1983 Black 300 D (donated to charity)
1993 Teal 300 D (160K) Sold
"I love the smell of burnt diesel fuel in the morning, it smells like ....VICTORY"

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USMC 1973-1976

I have noticed the trend to thinner oils as well. I believe that car companies are doing this to help them with their CAFE averages.

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Ali Al-Chalabi

2001 CLK55
1999 Dodge Ram 2500 Cummins Diesel
2002 Harley-Davidson Fatboy
Merlin Extralight w/ Campy Record

That's all it is, the car companies are helping themselves out, not you. At last year's Philadelphia car show, I saw a V8 Ford Crown Victoria and it called for 5W-20. Why not just pour in WD-40. Personally I will take engine protection over MPG. Here is the BIG sign that these thin oils have no real protection. Read the label on a bottle of any 10W-40 or thicker oil, you will see the words maximum engine protection. You will not find these words on the watered down oils. For your car, I would use 10W-30 or thicker. Look at the owner's and see what the thickest oil can be used for the current outside temps.

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1999 MB SL500 (110,000 mi)
2004 Volvo V70 2.5T (220,000 mi)
2014 Tesla Model S 85 (136,000 mi)
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