srvince

Ok so in the mazda rx8 in the USA it says to use 5w-20 but while i have a friend in Germany who says they use only 5w-30 in his mazda rx 8 is there a reason for this and if not really is it going to affect performance or even gas mileage ( dont care to much about the latter).

StealthTL

iTrader: (1)

Pretty much everywhere but north america specifies 5w30.

5w20 was a fuel saving measure to get the absolute maximum mpg for the government requirements.

One downside is that 5w20 is not found commonly elsewhere, just here, so the rest-o-world can use 5w30, no problem. Since it isn't required, and it's quite expensive, it's not commonly sold outside NA.

People think that means that the 5w30 is the 'right' oil for the rotary, that 5w20 was a govmint plot and they know better, but it is actually a very good oil - the 5w part is the actual important piece, an overall thinner oil at startup - you never want to go with a 10w30.

10w30 is one of the 'natural' viscosities of paraffinic lube oil base stocks, you could find and measure an oil with no additives at all that would be close to 10w30.

So cheapo no-name lube usually is 10w30, and are a few sandwiches short of a complete picnic.

SAE 20 oil is thinner than the old slime your granpappy used in the Chevy, but consider that it -
circulates faster cold,
cools better,
passes thru the filter faster,
warms up quicker,
closes the filter bypass quicker,
circulates faster hot,
reaches working pressure faster,
uses less h.p. to pump,
returns to the sump faster,
releases entrained air quicker,
...I could go on.

One of the side benefits of 5w20 is that it is vrtually impossible to make using 1960's technology, so the cheapo brands can't make it. It requires a sizable proportion of hydrotreated (semi-synth) bases, the old lubes just will not stay 'in grade' for the duration of the SAE tests.

Bottom line is that 5w20 oil is fine, and 5w30 too - just make sure it is a reputable brand. Kind of hard after Shell bought Quaker State and Pennzoil.....

srvince

ok so am i going to see a performance difference or no. just wondering if one will be better than the other while living in California but with the car registered in Illinois

StealthTL

iTrader: (1)

Nope.

...but fresh oil always makes the car seem smoother to me!

monchie

Do not make this a complicated issue. If your owner's manual says 5w-20, then use that. You still could use other grade of oil, but not too thick. Newer engines uses lighter oil than older engines. Up to 40 grade is still safe to use on the rx8.

1.3_LittersOfFurry

iTrader: (4)

Here is some interesting information... https://www.rx8club.com/series-i-tech-garage-22/5w20-requirement-just-epa-strong-arming-68637/

"Australian owner's manual:
"

I use 10w-40, Worked fine for my FC's.