My owner's manual specifies 10w40 or 20w50 for my '84 13B engine. Any reason 15w50 wouldn't work, or even be the best of both worlds? Did 15w50 even exist in '84?
Thanks.
Hal

 

Nope, I ran 15W50 in my FD for years, it will be fine.

The key is using good quality oil suited to your weather.

 

+1. And change intervals should be a little closer together than what you might be used to in a piston engine.

 

Change interval closer in miles, or time? My car hardly gets driven. It's an '84 with only 27,000 miles. Thanks.

 

Both - change every 3000 miles or, if you don't drive that much per year, change it at least at the start and end of summer if you store it over winter. If you plan to park the car for extended periods (ie more than a couple of months) there is a lot of good information on how to do that here:

How To Store Your RX-7

Remember - oil and filters are cheap insurance on a rotary.

For example, I changed my oil twice in 2016......I only drove 500 miles. It may seem paranoid but at least if the engine dies and I need a rebuild I will feel better knowing I did what I could to prevent it.

Tom

 

I meant miles, but don't disagree with the time aspect either. Sounds like a nice, real survivor.
Assuming this is your first rotary ... know that in stock form the engine injects a small amount of engine oil into the intake chamber of the engine. This is done to lubricate the hard seals (apex and side) and aid compression. That oil is eventually burned. It's not an ideal system since the oil will have contaminants. It's also VERY common in my experience to have a little fuel dilution of the oil over time in a rotary. That's why I recommend changes a little more often.

 

Is that synthetic oil?

 

Please don't open the synthetic vs mineral oil can of worms!

But to answer your q, i assume you can get both...i ran 15w50 mineral oil....and still do...

 

Can of worms?..This subject could have a whole separate category in the Forum as NOBODY dares to read the other 4 Thousand threads started about it!

I use Baby oil on my car so anything I hit Slides right off!
(anyone seen my wife?....)

 

What kind? Conventional oil in 15W-50 viscosity is pretty much non-existent outside of the aviation industry, and you sure as heck don't want to put aviation oil in your car engine.

 

Sorry my bad, I ran 15W50 Castrol mineral oil when I lived in NZ, super easy to get it from the stores there.

Couldn't find it when I moved to Canada so now I am running 20W50 Castrol mineral oil, available pretty much everywhere.

Tom

 

Agree that 15w-50 as a fossil-derived product is hard to find so I have been using either 10w or 15w - 40 - - with the latter being widely available as a 'diesel-quality'. Remember, you can use a high-performance grade/quality oil (such as labelled for Diesels or Turbos) in a 'lower-performance' engine, but, do NOT use 'standard-quality' oil in higher performance applications. Just because it is labelled for DIESEL engines does not mean you are only allowed to use it in such applications. It is same 'logic' as when choosing other fluids such as coolant, brake, and gear/diffs. Now, having said this, does any popular company make a TALL or WIDE filter that has same bottom config. as the OEM style (Fram) 3593? Not quite sure of number as car covered for winter and I don't have a spare to look at. I used to get the taller (PH73?) or whatever number, from '84-ish VW Scirroco. (or however it is spelled), but cannot find it on any shelves.

 

... which is why you need to read the API donut. If it only has a "C" rating, then DO NOT use it in a gasoline engine! If it has a "S" rating then it is fine to use in a gasoline engine.

Anything with a "SN" API rating is rated for turbos, so you don't need to worry about whether the marketing guys printed "turbo approved" somewhere on the bottle.

Most of the major manufacturers make a taller filter, but the general consensus is that the best filter for a street car is the OEM Mazda filter with the proper bypass valve.

 

Every oil container I have looked at lately displays both the S and the C rating specs. Many enthusiasts go more with 'brand-loyalty' - since vast majority of oils on market have up-to-date or acceptable specs for overall usage.
As far as the pros and cons of running synthetics, advice is to ask those 'in the know' for their advice and reasons. That is one question I asked the experts at <atkinsrotary.com> when I drove there in March of this year.
Thirty years ago I was getting my answers from Racing Beat - - - today it's from Atkins.

 

Since Mr. ebody brought it up, so others don't have to ask this is what those two shops recommend (from their respective sites)...

From Atkins...
What sort of oil should I use synthetic or petroleum based? What weight, and how long does it take the engine to break in?
You should not use any synthetics while breaking in the engine for the first 6,000 miles and keep the engine under 4,000 RPM for 1,000 miles. After that we recommend Ams-Oil, as this is the one we have done the most testing with. A 20W-50 should be used in the summer and a 5W-30 or 10W-30 should be used in the winter

From Racing Beat...
---> Rotary Tech Tips: Synthetic Oils And The Rotary Engine

Oil Viscosity
When selecting engine oil viscosity, we offer these considerations. First, if your vehicle is stock or near stock, follow Mazda's recommendations. For street or light racing use (autocross or occasional drag racing) with a substantially modified engine, it may be wise to move up to a 10W30 oil. For normally aspirated racing, 10W40 is appropriate, and for turbo racing, you may need 20W50 to maintain oil pressure at high oil temperatures. Just a word of caution : The higher the viscosity, the slower the oil circulates through the engine. This is particularly of concern in rotaries, where the rotors are cooled internally by oil sprayed from 2 jets in the eccentric shaft. If you choose too high a viscosity, you will actually decrease cooling flow to the rotors.

 

20W-50 Castrol gtx

 

I've used Redline "Synthetic" 20W-50 for years and I've had no problems.....