What's the true capacity of the engine oil system? Much of the marketing material (Mazda web sites, the RX-8 book, etc.) all indicate over 7 quarts/litres capacity - which would be OK with me. However, the RX-8 owners manual lists the capacity with filter change at 3.7 quarts for an oil change! So which is it, or am I missing some trick?

Regards,
Gordon

 

just a guess but alot of the motors i work on will only hold x amount of oil at a oil change with filter but after complete rebuild holds 1.5 to 2 qts extra.i guess we will just have to drain and see how much comes out.also im not sure if the rx8 has a oil cooler but if it does it would hold a bit.

 

Huh? How does a rebuilt engine all of a sudden hold more oil without increasing the oil pan size or changing the engine size? What does that have to do with his question?

 

A normal oil change does not replace the entire contents of the lubrication system. The oil filters, lines, and some galleries do not drain into the sump under gravity, so when you remove the drain plug you're not emptying the entire capacity.

 

I see.. either way though that's a big range between 3.7 and 7.1. I'm curious too, which is it?

 

Both, 7.1 total, 3.7 on an oil change. Don't forget the big oil radiators in the front of the car!

 

Which IMHO is truly frightening as that means with any given oil change you're only changing around half the oil in the car, so your actual oil change interval then works out to be (interval * 1.5) or so...

 

I agree - if capacity is really 7.x but only 3.7 drains on an oil/filter change, then you're only changing half the oil. That wouldn't be a good thing! I'm hoping there's an error somewhere...

Regards,
Gordon

 

this can't be right.. How would that make sense?

 

I'l bet their is a typo somewhere. The first car I bought was a 96 Mustang. That was the year ford went from the 5.0 to 4.6 liter V8. The car manual said 5 quarts. After a 1000 miles I had the oil changed at the dealer and when I got in it to start after paying the check oil light came on. They added some oil and the next day I brought it back and watched them change it again (it imbarressed the service department). Well we put 5 quarts in and let it sit. Sure enough after it sat and the oil finished draining from around the level sensor the check oil light came on. We looked at the service manual and it showed 5 quarts. Finally one of the senior techs pulled the top level troubleshooting guide and it said 6 quarts. About a month later I got a sticker in the mail that was to be put over the page in the manual so that it showed 6 quarts. Long story short they had a typo that got carried for a while and it took a few service departments calling before they knew where the mistakes were made.

 

I had my oil changed after about 845 miles. I know that some people say that its a waist of time and money but I haven't lost an engine yet doing this. It certainly can't hurt. I am sure their is a small amount of debris in the oil after wearing all the components in. Anyway the put in about 4.1 liters of oil. I checked the oil after I got it home and it was right at the top. I was thinking if the oil coolers each hold a quart and the rest of the system lines hold some you might only get 2/3 of the oil out during a change. Still it is curious to keep that much oil in the system.

Have you looked how small the oil filter is. Its the smallest oil filter I have ever seen and the car has one of the larger oil capacities I have seen. I guess its all part of the rotary world which is new to me.

 

3.75 US quarts for me.

Vince

 

I just checked the Canadian brochure and it claims that the engine oil capacity is 6.0L for the 4AT and 6.7L for the 6MT. This is surly got to be a typo; also, since when does the engine oil capacity change due to different transmissions. My manual is in the car right now but I recall it being ~ 3.7L with filter.

 

Since the standard-power engine only has one oil cooler while the high-power engine has two. Apparently the extra cooler and lines hold a further 0.7 litres.