Premix in engine oil

[R1DSO]

I just did something stupid and topped up my engine oil with 200ml of premix .

In my defence, the Idemitsu premix I use looks pretty similar to the Idemitsu 10w30 Racing Rotary engine oil I've been topping up with:

Premix.jpg

Engine oil 2.jpg

By my calculations, my engine oil is now just under 3% premix . I know premix is designed to lubricate (and ignite in) the combustion chamber, so I assume it's not as good at lubricating the rest of the engine's internals. Project Farm says otherwise, but that was in a lawn mower and not a rotary :



My question is, is 3% a negligible amount of premix to have in my engine oil, or should I do an precautionary oil and filter change to flush it out? The car had a (presumably single/5l) oil and filter change from the dealer I bought it off back in February 2020, under 2k miles ago using QX5W30C3. The previous year's oil/filter change was less than 1k miles before.

The plan was to do a filter and double oil change in Feb 2021, or after the car had done 4k miles in my ownership - whatever came sooner. I was going to switch to Idemitsu 10w30 Racing Rotary engine oil with the double change, sticking to frequent single changes with the same stuff moving forward.

However, with a double change of Idemitsu costing £160 in oil alone, I'm less keen on the idea if my RX-8 needs a change now . Moving away from the rotary-specific brands, I know 10w40 is the preferred viscosity, with Millers Trident a popular and much cheaper choice.

Cheers,

Phil

[R1DSO]

I can't see 3% having any noticeable impact on the sump oils ability to lubricant the bearings etc.

I don't see a Sohn/Cofs on your mod list so that oil is also going to be consumed by the OMP, which might be improved by the addition of the premix, certainly it won't do that any harm.

As the oil level drops and is topped-up then the percentage of "contamination" will be further reduced.

Well worth doing the maths and asking the question, to which my opinion is "She'll be fine mate"

[delta0]

The latest Idemitsu bottles are so similar that I’m worried I would do the same. I have some of the red ones left so I would be tempted to top them up with premix.

[R1DSO]

I can't see 3% having any noticeable impact on the sump oils ability to lubricant the bearings etc.

I don't see a Sohn/Cofs on your mod list so that oil is also going to be consumed by the OMP, which might be improved by the addition of the premix, certainly it won't do that any harm.

As the oil level drops and is topped-up then the percentage of "contamination" will be further reduced.

Well worth doing the maths and asking the question, to which my opinion is "She'll be fine mate"

Nice one, thanks Dave . Reassuring to hear that I’ve got a little longer before I make a call on whether I really do stump up the cash for a double Idemitsu change. I like that idea that it’s a rotary-specific oil, but not that I’d need to buy 10x expensive 1l bottles .

I was under the impression that you couldn’t fit a SOHN on an R3 engine. If I could, that mod would definitely be on my ‘to do‘ list, along with the oil filter temperature gauge which I think is the preserve of S1 owners also.

[R1DSO]

The latest Idemitsu bottles are so similar that I’m worried I would do the same. I have some of the red ones left so I would be tempted to top them up with premix.

That’s a good idea. I started buying Idemitsu after the change from red, unfortunately.

To try and keep things separate, I store my 2 stroke in the car’s door compartment in premixing bottles and my engine oil in the velcro pack in the car’s boot. However, I still managed to blindly go and grab my reserve 1l of premix when topping up today .

07842BA0-39EF-4E4F-8D7F-64D929CB1D62.jpeg

[R1DSO]

I was under the impression that you couldn’t fit a SOHN on an R3 engine. If I could, that mod would definitely be on my ‘to do‘ list, along with the oil filter temperature gauge which I think is the preserve of S1 owners also.

Sorry, no you can't fit a Sohn on an R3 because of the totally different OMP design.

The relocation of the oil filter also makes a sandwich plate tricky, though others have managed it, for oil temp and/or pressure.

Sent from my SM-G800F using Tapatalk

[PaulAV]

If your paranoid about the pre-mix with your engine oil, you could do a cheap engine oil swap, I tend to use Castrol 10-40 and purchase it from Tesco's when on offer.

[R1DSO]

If your paranoid about the pre-mix with your engine oil, you could do a cheap engine oil swap, I tend to use Castrol 10-40 and purchase it from Tesco's when on offer.

Given how cheap the Rotary Revs recommended Millers Trident 10w40 is still selling on Demon Tweaks for, I might just opt for that.

https://www.demon-tweeks.com/uk/millers ... l-2006317/

I saw New Duke posted regarding weights, although the post seems to have mysteriously disappeared ...

I went down an oily rabbit hole researching brands, weights and specs when I first got my RX-8, before coming full circle. Whilst frequent changes with organic oil would appear to be the preference, it seems that you can only get semi or fully synthetic engine oil from the reputable brands here in the UK.

In addition to the marketing, my train of thought was that Idemitsu, being a rotary specific synthetic oil, is designed to burn cleanly in the combustion chamber. Its standard product 10w30 viscosity is the same spec as used by other rotary brand Synionic and this has been developed to run in hotter rotaries (RX-7s) in hotter climates (Japan).

So, I would have thought it should sufficiently lubricate the gear bearing etc, especially with our UK-spec twin oil coolers keeping temps down in our mild climate. Or, Idemitsu would have changed the spec, given that they’re not wedded to Mazda or the efficiency criteria of other manufacturers.

However, that’s just where I ended up. I am by no means an oil expert . And, given the state of the economy currently, I’m starting to think that 10 litres of Millers Trident to do a double oil change at £32 vs £160 for 10 litres of 10w30 Idemitsu is too big of a price differential to ignore!

[delta0]

We run higher oil pressure in the R3 so this Idemitsu 10w30 is perfect.

[v-rex]

However, that’s just where I ended up. I am by no means an oil expert . And, given the state of the economy currently, I’m starting to think that 10 litres of Millers Trident to do a double oil change at £32 vs £160 for 10 litres of 10w30 Idemitsu is too big of a price differential to ignore!

I bought 10 litres of Millers from Demon Tweeks, a 5L and 5 1L's for top ups ( I like these as I can keep them in the boot). Josh at TPS did talk about another oil they do which is Synionic 10W30, another one for rotaries, and I did consider it but it is pricey. I don't think he leaned particularly to either of them, but did say Miller's is their defacto choice and it's never caused a problem so far. I think some people also make the point that frequent changes are maybe as important as the type of oil you use, and at the prices Miller's is you can comfortably change pretty frequently !!

[v-rex]

I've heard that when the last stocks of Synionic oil is sold in the UK there is unlikely to be any more. The volumes now being sold have made it uneconomic to produce any longer, apparenty.

[New Duke]

I saw New Duke posted regarding weights, although the post seems to have mysteriously disappeared ...

Yeah I decided against leaving the post up. Hope you find a solution that you're happy with.

Just to add a clarification. That Idemitsu isn't fully synthetic. It's a semi with a mineral oil base. Just like all the cheaper oils that do exactly the same job.

It's all there in the technical data sheets instead of the advertising blurb.

We run higher oil pressure in the R3 so this Idemitsu 10w30 is perfect.

Higher pressure and injector spray patterns don't change hot viscosity or mitigate oil shear though. I wouldn't call any 30 weight mineral base oil perfect for rotaries that are driven properly in summer.

[R1DSO]

At only £3.20/l for the 5l bottles, I just couldn't resist the Demon Tweaks Millers Trident offer given it's reputable stuff - the offer looks like it's running until the beginning of October, FYI. £16.99/l for Idemitsu is a BIG premium, especially when talking double changes and when there are mixed opinions on whether it's viscous enough.

I've ordered 15l of Millers 10w40 semi synth + a 1l bottle for the boot pouch. The 1l bottle looks different enough to Idemitsu Premix (which I'll continue using) for me to hopefully not top-up my engine oil with the latter again :

https://www.demon-tweeks.com/uk/millers ... l-2006317/

Once I've got through topping up with my dogend of 10w30, I'll do a double oil change with the Millers. I needed to order more engine oil to top-up with anyway, hence the change of direction in viscosity now given the price of Millers vs buying further 10w30 Idemitsu top-ups. I've also ordered an OEM Mazda R3 oil filter, a pack of crush washers and a GReddy magnetic oil drain plug.

The double change will be around the 2k or so miles mark since the last (single) 5w30 oil and OEM Mazda filter change. Moving forward, I'll plan on doing single oil changes with Millers every 3k miles to keep things fresh. What are the thoughts on changing the filter each time with these low intervals vs every 6k miles i.e. only fitting a new filter every other single oil change?

[New Duke]

I change the oil about every 3-4k. Given that the filter is only £10-12 from dealerships (and the washer about a quid) I change it every time. But that's because I have to get down there to drain the sump anyway. I've never gotten the hang of vacuum pumping the oil out of the top of the 8 without spraying it everywhere. If I had I'm sure it'd be tempting to skip some filter changes.

Lots of folks here do only change the filter every other oil change. So either way you won't be alone in your decision. The best thing you can do is change the oil frequently, regardless of what oil goes in, especially if you use the car on track. So good call on that

[v-rex]

... the offer looks like it's running until the beginning of October, FYI.

Awesome, that's useful info. I might pick up another 5L or two for future changes, and it looks like I have a month or so to think about it.

[delta0]

I saw New Duke posted regarding weights, although the post seems to have mysteriously disappeared ...

Yeah I decided against leaving the post up. Hope you find a solution that you're happy with.

Just to add a clarification. That Idemitsu isn't fully synthetic. It's a semi with a mineral oil base. Just like all the cheaper oils that do exactly the same job.

It's all there in the technical data sheets instead of the advertising blurb.

We run higher oil pressure in the R3 so this Idemitsu 10w30 is perfect.

Higher pressure and injector spray patterns don't change hot viscosity or mitigate oil shear though. I wouldn't call any 30 weight mineral base oil perfect for rotaries that are driven properly in summer.

I’m not aware of any issues with people running Idemitsu, a rotary specific oil. This particular one is fully synthetic. I wouldn’t recommend other oils.

[New Duke]

I’m not aware of any issues with people running Idemitsu, a rotary specific oil. This particular one is fully synthetic. I wouldn’t recommend other oils.

No, it's a semi sold as fully synthetic. Oil labelling is a murky place.

Bottom of page 2 on the attached data sheet from Idemitsu. It's a semi made from mineral base stock. Just like all the cheaper semi oils available.

The Idemitsu costs more because it's shipped over from the USA... and for hype. It won't cause anyone problems, but it's just oil.

[delta0]

I’m not aware of any issues with people running Idemitsu, a rotary specific oil. This particular one is fully synthetic. I wouldn’t recommend other oils.

No, it's a semi sold as fully synthetic. Oil labelling is a murky place.

Bottom of page 2 on the attached data sheet from Idemitsu. It's a semi made from mineral base stock. Just like all the cheaper semi oils available.

The Idemitsu costs more because it's shipped over from the USA... and for hype. It won't cause anyone problems, but it's just oil.

I believe it is from Japan, but yes that will certainly add to the cost.

[R1DSO]

I change the oil about every 3-4k. Given that the filter is only £10-12 from dealerships (and the washer about a quid) I change it every time. But that's because I have to get down there to drain the sump anyway. I've never gotten the hang of vacuum pumping the oil out of the top of the 8 without spraying it everywhere. If I had I'm sure it'd be tempting to skip some filter changes.

Lots of folks here do only change the filter every other oil change. So either way you won't be alone in your decision. The best thing you can do is change the oil frequently, regardless of what oil goes in, especially if you use the car on track. So good call on that

Nice one, thanks mate . Yeah, I have no issues with regularly crawling under my car, so I may as well change the filter at the same time.

Unless running a magnetic filter, I would have thought that gravity would help particles out more easily with the oil when draining from the pan too. And, although its surface area is small, a magnetic drain plug should help collect up some swarf too.

[R1DSO]

I change my oil frequently and alternate between conventional "drop the sump plug" with a filter replacement, and "suck out the top" just to refresh.

I have a magnet on the plug and super magnets around the filter. Both help collect ferrous particles but do nothing for any bearing wear material.

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[R1DSO]

I change my oil frequently and alternate between conventional "drop the sump plug" with a filter replacement, and "suck out the top" just to refresh.

I have a magnet on the plug and super magnets around the filter. Both help collect ferrous particles but do nothing for any bearing wear material.

Sent from my SM-G800F using Tapatalk

Good to know, thanks Dave . Out of interest, when doing an initial double change (on the same day), is there any merit in changing swap oil filter after the first vs the second oil drain?

[R1DSO]

I replace the filter on the second change, as the first dose of fresh oil will have got more debris into circulation.

Also you don't want the filter already contaminated with the 50% old oil mixture.

[R1DSO]

I replace the filter on the second change, as the first dose of fresh oil will have got more debris into circulation.

Also you don't want the filter already contaminated with the 50% old oil mixture.

Got it. Makes sense . Thanks Dave.