Javafuel

For whatever reason, 5W-20 is a rare commodity in LA gas stations. I stopped by 4 different gas stations and none of them have 5W-20. 5W-30 is pretty common, what is the difference between the two? Can I use 5W-30 instead? Thanx.

eccles

The numbers refer to the viscosity of the oil at different twmperatures. Both will be as thick as a 5W-weight oil at 23°F, but they will differ slightly when hot, with the 5W30 being slightly thicker (equivalent to a 30-weight oil at 212°F instead of the 5W20 being equivalent to a 20-weight). Check out this page for more information.

I believe that Mazda specifies 5W20 because it marginally improves fuel economy because the thinner oil does not take so much effort to pump around, but the difference is minimal at best. Personally, I had no qualms about using 5W30 when I had my oil changed.

shift_zoom8

I live in Los Angeles also and I found plenty of 5W-20 Castrol and Pennzoil (individual quarts and 12-quart boxes) at Wal Mart.

RobDickinson

UK spec calls for 5w-30 in the RX-8, btw.

Nubo

The wider the range between the Winter and Summer viscosity, the more modifiers have to be added to the base oil to achieve that effect. You are better off with using the narrowest range that suits your vehicle requirements and driving conditions. There are other reasons for manufacturer to specify particular weight. One of course is fuel economy but there can be others such as oil film shear strength that may have particular importance in a rotary vis-a-vis the apex seals. There's also pumpability, which could also have significance for the rotary since it uses oil injectors in the intake. These qualities are related to viscosity.

Why are you concerned about what gas stations carry? Buy in quantity at a parts store or department store. Keep an eye on oil level so you can take care of it in the comfort of your own garage instead of being surprised at the gas station. Carry a quart or two in the trunk if you're going cross-country.

On the other hand, I wouldn't hesitate to add a quart of 5w30 if the car needed oil and that's what was available. I'd just try to avoid that situation though. I don't think I've purchased a quart of oil at a gas station in 20 years.

eccles

Heh, many moons ago we had a newbie member of the Mazda Car Club of Australia who trashed his motor because he had been told only to use a particular brand/type/grade of oil, and couldn't find any at the gas stations he kept stopping at. Rather than toss in a litre of something close, he kept driving it hoping to find the "right" oil. It was an expensive lesson.

Javafuel

Thanks for the info, guys. I picked up a 12pk of 5w20 from the local Pep Boys. Gas station is just more convenience. BTW, the oil dip stick is hard to read or what? I mean the color of dip stick is the same color as the motor oil...genious

How often do you guys add motor oil? How much to add? My oil pressure gauge didn't change (or change very little) after the oil is added. Maybe I should add more...

eccles

If your oil pressure gauge ever moves, you have cause for concern. That's because it's not a true analog indication of pressure, but a glorified "idiot light" that indicates whether the pressure is above a fairly low threshold. If it ever moves from just-over-halfway, it'll be to drop to zero, and you'd better be quick with the ignition switch if that ever happens!

jtdwab

I hate the dip stick to. The only way I can get an accurate reading is to lay it on a paper towel and move the stick a little and see where the oil soaked into the towel at. Its a pain. I miss the classic flat piece of steel. those old sticks were easy to read.

AlexCisneros

Has anyone used Redline's SAE 20 (5W20)?

Pros/Cons of using synthetic race oil?

XUrotaryrocket

i use 5W-30 with no negative effects to gas mileage. i drive alot of highway miles so my mpg is always above 20. i am a firm believer that the extra bit of viscosity will help the longevity of your motor.

Javafuel

The gauge does move, I remember the oil pressure was at about 3/4 when I drove off the dealership. After 1500 miles, it's now at about 5/8. But it stays at 5/8 after I added some oil. It should go back to 3/4, right?

Javafuel

That's a good tip, thanks.

Nubo

No, there shouldn't be a change in oil pressure after adding oil, assuming it was not ridiculously low on oil The oil pump pressurizes the system. It doesn't know how much oil is in the crankcase as long as there's enough to keep pumping. One possible exception would be if you added an oil of very different viscosity.

Similarly, your fuel pressure doesn't go up when you add gas.

Javafuel

Hmm...so my 8's oil pressure shouldn't have gone down the first place. But it did go down about 1/8. Does that mean I should have it check out? Can you guys tell me your oil pressure level? Thnaks

sferrett

My oil gauge reads 2 ticks to the right of the center line. It's always read that and I believe (from looking at the dashboard self-tests) that's the maximum value that particular gauge can display...

Javafuel

Mine reads about the same right now, 2.5 ticks to the right of half line. But it dropped about 2 ticks since I got this car.