RX-8GT

Hi,

I am a new owner and I never had to add engine oil in the cars I owned.

So, here is my dumb question.

I know I am supposed to add engine oil. But does it have to be the same brand of oil my dealership will be adding when I bring in my car for service?

Thanks in advance.

MI_FamilyMan

Nope. Not if you are using the recommended 5W20 non-synthetic. The problem I have with checking/adding oil is that darned dipstick is impossible to read.

Over about 2,000 miles thus far, I've only added a quart, and that was because I got paranoid reading all the threads on this board. I'm topped up now.

RX-8GT

I just bought a bottle of Castro GTX 5W20 though I am not sure if it's non-synthetic. I remember seeing someone mentioned it in another thread.

Yeh, not only it's impossible to read, it's difficult to reach, too. Why couldn't they make it easier since we need to do this for however long we keep the car.

By the way, I am a CA family man

Thanks.

MI_FamilyMan

Nice. I don't think GTX is synthetic. Castrol's version of "synthetic" oil is normally labeled Syntec. I think you're good to go... once you figure out if your oil level is in fact low.

Magic8

There are couple of threads on synthetic vs. non synthetic. There are a couple of people that performed oil analyzes. The basic conclusion is that the 5W20 seems inadequate and should move to 5W30. Other REgion of the world and I think in the US use 5W30 in their 8's.

RX-8GT

OK. Then I guess my question is what will happen if I add 5W30 into the existing 5W20 which I assume already in my car and the dearship will be adding when I bring in for service. Will 5W30 void the warranty since Mazda designated 5W20 in the users manual?

I did not mean to start a thread that everyone else seemed to know already. I did try to read those threads but found myself lost and puzzled and there are some many things that are too technical for me.

I appreciate all of you who took the time and replied to the thread.

Go48

Generally you want to add what the owners manual recommends. Will topping up an engine containing 5W20 with 5W30 hurt anything? No. As long as the oil is the same spec, adding a little of a slightly different weight will not be a problem. For the recommended oil ratings see the owners manual. Ratings are those little markings on the oil bottle, like SL, ILSAC and so on.

Also, you might want to ask the dealer what weight oil he uses when he changes your oil. Based on some postings on this forum, it is apparent that some dealers don't necessarily follow the manufacturers recommendations.

Magic8

The dealers will have to go through a lot trouble to find out you have non-5W20 in your engine. I wouldn't worry about the warranty issue. Heck some people use 5W50 synthetic if they do a lot of track driving.

bxb40

Someone from Australia posted a manual page showing you can use a wide variety of grades in RX-8. The criteria is the driving style and local temperatures. The 5W20 oil has to do ONLY with the fuel economy Mazda claims (not the one we see ). Anybody can use 5W30 (this is what is used in Japan and the car was developed there). During the summer month, 5W40 (expensive) or 10W30 (cheapest). As for synthetic vs. blend vs. dino - way too many threads already, so I am not even going there.

My recommendations:

All year except winter: Kendal GT-1, and the 2-3 month of winter: Mobil 1 Trisynthetic or Supersynthetic, if going 5W30.

Or, Kendal GT-1 Blend, Sunoco Ultra Premium or Havoline year round except winter, and Coastal Premium for winter, if staying with 5W20.

These are based on performance criteria: stability at high temperature under high shear (HTHS) - can you say Renesis? , low deposits (TEOST) (we inject it in the combustion chamber!) and viscosity at low temperatures (CCS, MRV-TP1) ( -35C, maybe irrelevant for most of the US).

Danielson

Well, if you read your manual, it is well indicated not to use SYNTHETIC oil with the rotary engine !

Go48

WARNING: Put on your flame suit now before it's too late!

The owners manual says nothing about not using synthetic oil, at least the manual that comes with the US car. However, there is a little fold-out pamphlet (see attachment) in the owners package that, among other things, instructs the owner to "Add only non-synthetic 5W20 engine oil....". So your premise is correct but your precision is flawed. :D

TRU681

What page that the manuel said not to use synthetic because I been using synthetic whenever I get my oil changed at the dealership?