Huh? We produce the same power in a smaller volume of space. From where comes "cooler"?

I have to disagree with you here.

5w-20 offers weak ass protection, thinner = weaker strength = easier metal to metal contact = no good. Only good thing about 5w-20 is you probably get like another couple % better mpg. thats about it. You're pretty much giving up engine life for if "you can notice" mpg increase.

Even Castrol admits it.

Engine life - Something = or higher than 5w30
Every single bit of MPG - 5w20.

5w-20 should not be used if engine life is your major concern.

Plus, since when did Rotary engine runs cooler than piston cousins?

Come on guys, we all know there's less thermal mass in our rotary than a comparable power piston engine. Again, one of the reasons we get poorer mpg.

I'm not saying 5w-30 isn't better, but we need not scare off folks who go with dealer mandated 5w-20. Better to have them change oil frequently.

Oh, and I go Castrol GTX as well.

I have always used Castrol GTX 5W-30 all year round redline 1st 2nd and even 3rd on the freeway on ramps use ide premix and have no carb buil bup that I can see coming out the back of my exhaust. That dont mean its not building up inside my engine.

Did you not read your manual....show it to your dealer!

"Engine oil viscosity, or thickness, has an
effect on fuel economy and cold-weather
operation (starting and oil flow).
Low-viscosity engine oils can provide
improved fuel economy and cold-weather
performance.
But high-temperature weather conditions
require higher-viscosity engine oils for
satisfactory lubrication

My 2005 manual specifically cites "5W-20" on page 8-13, so showing it to my dealer would be pointless.

So I don't and change my own. ;)

Doesn't your manual also say "or 5w30 under certain circumstances?" or words to that effect ?(your manual is different from mine)

I thought it was mentioned.....

S

The manual also tells ya that, it really depends on your local condition, and you can use anything that fits your area.

Still not sure what you mean by that. The engine weighs less, that's true. That in itself doesn't necessarily make it cooler or hotter so I'm not sure what you're getting at with "less thermal mass".

The Wankel engine produces remarkable power for its size (mass) compared with piston engines. However, that relatively small mass is also a disadvantage as all internal combustion engines are more efficient when fully warmed up (e.g. highway speeds for long duration). There's plenty of thermal dynamics info out there on the Wankel and its effect on gasoline efficiency.

Interestingly, at one point the Wankel was able to pass emissions regulations w/o a cat, but at the expense of even more fuel consumption. Perhaps we'd all be happy with 10 mpg but no cat. ;)

Page 8-12 of my '06 manual has a paragraph headed "Recommended Oil." The first line of the paragraph, in bold, says "Use SAE 5w20 engine oil." The pictorial with the thermometer shows 5w20 for all temperatures. There's no waffling about it, no discussion of situation dependence.

So the manuals do change from year to year.

Ken

that also means they're just generalizing it.

the rule is, use what you want.

Or taking a bigger swig of Kool Aid.

Gasp! Not follow the manual? After Mazda went to all the trouble of printing it? Not just once, but a revised version every year?

Ken

They change their warranty as well , at least for Basic warranty :P

04-05 50 K miles / 48 months

06+ 36K miles / 36 months :lol:

they probably found out "aww crap 5w-20 is craping our engines, lets make the basic part shorter so we carry less liability" :lol:

'06 still has the 50k/48 month warranty. They shortened it to 36/36 in '07.

But all 8s have the 60 k /60 month powertrain warranty, and the 8 year internal engine part warranty.

So the shorter bumper-to-bumper (which I believe applies to all Mazdas) has nothing to do with oil specifications for the 8. It's probably to cut their losses on sunvisors, squeaky brakes, etc.

Ken

So does the '04 AT come only with one oil cooler? Should I do to the dealer to have a 2nd one added on or should I just go to outside shop to do it.

As for my compression problems, is it due to carbon build up? What is the cheapest but most effective product to use to clean it? Is there something I can just ass to my gas or do I need to take it fora tune up to get it cleaned.

Lastly if I do use W50 of W60 will this really affect my MPG a lot or is it not noticeable since I'm already getting bad mileage anyways.

'04 AT has one cooler. If you want to add another, going to a dealer or an independent shop or doing it yourself is just a matter of cost and who you think will do it right.

If there's carbon buildup, this is Mazda's method for cleaning it out:

http://www.finishlineperformance.com...4-08-1924f.pdf

There are posts on this site about doing something similar with other products. Search for "sea foam" or variations of "de-carbonize" for those posts.

Personally, I would not use a w50 or w60 oil. 5w20 may be too thin, but 50 or 60 is a huge jump from what Mazda recommends.

Ken

Ken,

Thanks for the info. I will be sure to search this site. For the Oil cooler since it only came with one where would be the place the mount the 2nd one and do you know how much it will cost me to have it done outside.

The second would mount on the other side, the way the MTs come. I've got an MT, so I had two from the start. No idea about the cost...hopefully someone who knows will pipe up.

Ken

Huey52 - take a gallon of water and microwave it for 1 minute. Do the same for a tablespoon of water. The thermal energy input is similar. Which one gets hotter?

I think the "kit" will cost about 700 something USD. If you buy it within the US

its pretty much plug and play. you can do it yourself if you know where to look for.

I have been using 5w20 per the manual for the first 24,000. I am now considering switching to 5w30 after reading these threads. My only concern is a dealer trying to get out of a warranty claim if I didn't use the "recommended" oil. Has anybody heard of this happening?

remember, recommended is NOT the same as required.

if its REQUIRED, then you might have a problem

but its just RECOMMENDED oil weight, so you can use something else other than 5w20.

Heavier oil can keep the metal to metal contact to a minimum.

I personally use 10w40.

Actually, there's no thermal energy imparted by the microwave (RF) energy itself, but rather by the excitation of the water atoms/molecules themselves, but I see where you're [trying to] go here. ;)

I've been discussing the relatively low thermal mass of our rotary engine, compared to a similarly HP-rated piston engine, and its effect on fuel efficiency. Volumetric vs. thermodynamic efficiency. A different can of worms.

soif you have a warranty claim are you going to blurt out that you used an oil they didn't recommend ?