Oil Type to use 1987 Rx7
 

Hi everyone, I do not remember what type of oil my 1987 Rx7 uses. I'm not sure if it is a 10w30 or a 5w30 regular oil not synthetic.

I appreciate your help on this.

Thanks,
Harold

Neither really. Most will say they use 20w-50. I've been using 10w-40 for years. Here is a screenshot of the chart from the owner's manual. 5w-30 isn't even an option really and 10w-30 is only good to outside temps of about 80 degrees F. If it doesn't get below 20 degrees F the 20w-50 would be fine. 10w-40 has the broadest temperature range on the chart but is getting harder to find as is the 20w-50. I am thinking about switching to a 15w-40 diesel oil like Shell Rotella on my next change.
https://cimg1.ibsrv.net/gimg/www.rx7...7e31c66d6b.jpg

I've recently started using Costco Kirkland 15w-40 Diesel oil at $40 bucks for 3 gallons. Seems ok. Not synthetic, so I change at or before 3000 miles.

the cool thing about the Rotary is that it doesn't care too much about what oil you use. it cares more about how fresh it is.

the manufacturers are going away from having a temp chart like that, the engine runs at the same temp kind of no matter what its like outside...

You know as I was looking at that chart yesterday, I was wondering. Since the engines operating temp is well above ambient how does that have an effect on which oil grade you use. I understand the cold temp as that has to do with how the oil flows when cold and cold start protection. If I understand correctly the second number is what weight oil the oil behaves like at temperature due to the viscosity modifiers applied to the base weight oil (1st number), but I don't understand how ambient temp effects that.

Here's some info from a thread on Bob is the oil guy that explains the effects of ambient a little for anyone interested.
How does high ambient temperature affect oil ? | Page 2 | Bob Is The Oil Guy

Unless someone knows of an additive in diesel oil that leaves a residue that's bad for the apex seals behind when burned I think I am switching to 15w-40 Rotella.

so there are basically 3 things to look at to pick an oil. the easiest is the weight. lets just use a 10w-30, the 10w is the viscosity at some low temperature (i want to say 0c) and the 30 is the viscosity at operating temp (i want to say 50c)
basically you follow the spec here, if you look at the chart, from 0c to 30c Mazda says that 10w-30, 10w-40, 10w-50, 20w-40, and 20w-50, so basically anything.

the next thing is the "Performance Level" the American Petroleum Institute uses a 2 letter code starting with S, Mazda specs an SF which is really old, basically you want (and good luck finding anything else) the most current one, which is SM.
there is an SN and SN plus, which are for newer cars, its not really a problem because SN and SN+ are going to come in weights that aren't compatible. (0w-12, 0w-16)
Diesels are C

the third thing would be if Mazda asked for anything else, they usually don't. other makes have in house specs, sometimes part numbers, etc.

https://www.api.org/~/media/files/ce...glish_2013.pdf

I remember back in the day when asking what kind of oil to use in an rx7 would have you flamed so bad you wouldn't wanna come back... yall are so nice.

I exclusively ran 20w50 and my 86 N/A and it gave up the ghost at 267k miles. . . .And it failed because I didn't change the water enough which resulted in a corroded seal on the iron between the cooling channel and exhaust channel which led to pushing water into the overfill container due to pressuring the cooling system..

I live in CA bay area so the temps are what they are here.

Buy some 20W-50 and I guarantee the cashier at the auto parts store is going to say, "Whatcha putting that oil in?" 😆

this.

at some point after moving to Florida, i started using 20W50 only. i don't know when it happened, but now i use the 15W40. it's hot where i live though so i don't have to worry about first starts as much as i did when i was in New York. winter here is ... like ... 10.787 days, so it doesn't much matter.

I just changed to Mobile 1 full synthetic and it actually runs a little cooler than the Royal purple I was running, was pretty surprised, I still run OMP and premix a little too so I change my oil every 500 miles to keep ultra clean (only about every 2 years so I don't mind the extra $$)

synthetic bad!
 

I read online somewhere that switching to a synthetic oil on a rotary engine is not good for any of the seals, Something in the chemical makeup of the synthetic oil deteriorates these older type seals and will do the same to regular RTV sealent used on these engines. Permatex has a special sealant for use on engines that use synthetic oil.

I'm installing my third engine and will just use 10W-40 conventional oil, changing it out along with the oil filter every 6 months. That seems reasonable.