Using oils designed for diesels in gas engines

[digitalSniperX1]

Can anyone provide detailed information on the differences between the diesel engine oils vs. gasoline engine oils. I've read where the diesel oils (DELVAC) have performed very well in high performance gasoline engines. I'm considering it and perhaps AMSOIL DEO for use in my RX8, and yes, I know an RX8 engine and a big diesel are worlds apart. The RX8 is a big soot generator, and it's designed to burn oil. It's my understanding that the oils for diesel engines produce less ash in the combustion process.

Thanks for your input.

 

[JAG]

Look at the sulfated ash content of candidate oils. HDEOs generally have more of that than PCMO. There are exceptions of course. I'm not a rotary expert though so can't tell you what's the best approach on oil choice, whether to use a very dilute 2-stroke oil mix in the gas, etc.

 

[Dyoel182]

They hold up very well and have the extra zinc some people love to have. On my turbo mazdas I noticed a drop in oil consumption and less smoke when I really hammered on it.

 

[digitalSniperX1]

Originally Posted By: JAG
Look at the sulfated ash content of candidate oils. HDEOs generally have more of that than PCMO. There are exceptions of course. I'm not a rotary expert though so can't tell you what's the best approach on oil choice, whether to use a very dilute 2-stroke oil mix in the gas, etc.


Ahhh..then I'm mistaken, I thought they were lower in that regard. Good to know.

 

[digitalSniperX1]

Originally Posted By: Dyoel182
They hold up very well and have the extra zinc some people love to have. On my turbo mazdas I noticed a drop in oil consumption and less smoke when I really hammered on it.


Ok, so you see a benefit using them, specifically the increased ZDDP.
I'm guessing you're catless. I'm not there yet, but I am running Amsoil Saber pro in my gasoline, and I'm thinking it might put me there. I'd prefer to keep them, but I don't want to ruin them with what I'm doing in the oil and with oil in the gasoline.
I mix the saber pro with FP+. So far, engine seems to like it fine (first tank doing this). It's smoooth as silk and revs without any vibration (5k miles on the engine it's a 2007).

 

[FrankN4]

In my study of the use of diesel oils in regular gas engines, I have learned that the main differences is: diesel oils have more/better antiwear agents such as ZDDP------diesel oils MAY have more detergents--------diesel oils USUALLY(except for the so called High mileage gas oils)have more antioxidants------diesel oils have more sulfated ash--------diesel oils MAY OR MAY NOT HAVE friction modifiers. If I could find a good synthetic 5w30 or 10W-30 diesel oil with friction modifiers in addition to ZDDP, that would be my oil of choice.

 

[digitalSniperX1]

Does the increased ZDDP result in the increased sulfated ash. I'm not a chemist but I'm guessing this is the non combustable metallic component resulting in ash.

Keep in mind these rotaries inject engine oil into the combustion chamber.

 

[ericthepig]

Just repeating what I've read on BITOG - diesels oils will not hurt the cats unless you are burning significant oil - and even then the cats may not be affected.

Most of the diesel oils I've seen are designed for mixed fleet operations(indeed, many of the oils are API SM rated) - don't the gase engines in these "mixed fleets" have cats ?

Of course with your RX8, you might indeed be testing this issue given the oil consumption.

 

[digitalSniperX1]

I'm sure they do. good information.

 

[Dyoel182]

Originally Posted By: ericthepig
Just repeating what I've read on BITOG - diesels oils will not hurt the cats unless you are burning significant oil - and even then the cats may not be affected.


Thats been my experience. No cat problems to report on either vehicle.

 

[Winston]

Since they have more ZDDP than the SM oils, they will foul the catalyst faster. If that catalyst fails under warranty, the mfg will have a good case to deny replacement of the cat under warranty.

 

[Dyoel182]

Thats been the rumor but we dont have any proof of that.

 

[digitalSniperX1]

I think the Amsoil product I posted is SM rated. I think DELVAC may be also.

I'm already running about 4 oz/12.5 gallons of 2 cycle in the gasoline. I'm not sure what that does to cats. I should probably have the 2 cycle (Amsoil Saber Pro) analyzed.

 

[Greaser]

Been using HDEO for years on my gassers with great results.I have the UOA's to back my claims.

 

[digitalSniperX1]

Originally Posted By: Greaser
Been using HDEO for years on my gassers with great results.I have the UOA's to back my claims.


Why did you begin using them over the PMCO's?

 

[Doug Hillary]

Hi,
digitalSniperX1 - I have been using HD lubricants in my petrol engines since around 1958

The reasons? Their overall performance in almost every engine and especially those over the years that have some "Technical imperfections". Their TBN and detergency aspects were the early sellers for me!

I still use them today even though the average PCMO is of excellent quality and perform well in normal use and out to recommended service requirements

 

[digitalSniperX1]

Originally Posted By: Doug Hillary
Hi,
digitalSniperX1 - I have been using HD lubricants in my petrol engines since around 1958

The reasons? Their overall performance in almost every engine and especially those over the years that have some "Technical imperfections". Their TBN and detergency aspects were the early sellers for me!

I still use them today even though the average PCMO is of excellent quality and perform well in normal use and out to recommended service requirements


Hello Doug,

It was specifically your posted experiences with DELVAC that got me thinking about this. From what I understand these rotaries are persnickety engines, some of what I've heard is undoubtedly true while other information may not be.

I'm trying to figure out exactly what i should be doing to keep it running well and fend off an engine failure.

Thanks for the input. Much appreciated.

 

[Doug Hillary]

Hi,
digitalSniperX1 - In your case I suggest you closely follow Mazda's recommendations for your lubricant type and viscosity

Mobil recommend using their Synth S or Super S 10w-40 here in Australia and New Zealand. In the US they recommend Mobil 5000 Clean 10w-30

I would not use the likes of Delvac 1 5w-40 in your case

 

[digitalSniperX1]

So far I've been doing just that, with the exception of added oil to the tank (approx 350/1 ratio gasoline/2cycle)..

I'm using 5w20 Amsoil XL (mazda recommends 5w20 in the US). It's a GRPIII oil. Since most 5w20's contain this oil, I can't see a reason not to use it. Plus, others use PA0 synthetics with apparently no issues. The "no synthetics" rule comes from mazda with the disclaimer that they've not tested any of their cars with synthetics and cannot recommend them.

They are not forbidden though as Mazda co-developed a sythetic oil with Idemitsu for rotary application.


There have been a high incidence of engine failure in this car. Of course ultimately anything I do outside Mazda's recommendations are somewhat of an experiment, they do seem to be inconsistent.

The 5w20 being the largest inconsistency. In other countries, the engine oils recommended by mazda are 30 and 40 weight oils. It's said that Mazda tows the Ford line on this one...and i think ford recommends (for fuel savings) 20 weight oils in all its passenger cars.

 

[Doug Hillary]

Hi,
you are probably correct about "toeing" Ford's line

Viscosity is not SO important in these engines - clean burning characteristics are. Mazda knows what they are saying about synthetics. A fiend of mine is in the throes of selling his RX8 for a new high performance Mazda 6. His Dealer here is very adament about using the correct lubricant