just fyi, 15w-50 Mobil 1 is the same price as 10w-30 or other weights....thought that was common knowledge

 

Nope, I don't use Mobile products so why would I know their prices?

The fact is, rarely will you ever heat the oil up enough to really break it down fast on the street and require something heavier than a 30 weight. Take a look at rynberg's message who does have an oil temp monitor. At the temps you'll ever see on the street, 50 weights will be doing more harm than good.

 

Considering it costs $40+ dollars to fill an FD with gas, I don't see the big deal about spending an extra $20 every 2,000 miles for the better oil, even if it's overkill.

 

Well, considering it's much harder on the engine (i.e wearing out parts sooner) and can/will cause worse gas mileage since the car works harder to push it through.... IMO, those are maybe not "big deals" but something people should really avoid.

 

Viscosity maintanence over time between oil changes.
My rationale with the heavier weight 15w50 was to to try to counter the thinning properties of the fuel, which in my estimation quickly turns 15w50 into something more akin to 10w30. Especially a concern with the turbos.
But like I said, It's been a while since I've used 10w30 and I'll give it a try and see how it goes this next change. Your points about cold start-up, pushing it through some internals when still fresh, and lowering my already poor mileage is also a concern. Since I don't have an oil temp guage, those readings from rynberg were also interesting.

 

The weight really has more to do with how it stands up to heat, not necessary being dilluted with fuel. Tests are now showing that in normal cars, the lubricating properties of today's oils are lasting up to 10,000 miles (and longer in some cases) before they lose their ability. However, since our cars to end up with blow-by which dillutes the oil, we do need to change our oil more often regardless of the weight.

 

FYI... many racing teams use like 0w-20 oils for the track. Ofcourse, they change it after every race.

But I dont understand how people feel good about mixing up oil and thinking that they do good to the engine. Are you sure its good to mix up ? Or do you just feel it should be good for the engine ?

 

Porsche recomends 10W30 Mobil one on they're 100K + Twin Turbo Cayenne's, and they also tell you not to chance it more often than every 5K miles.

I think running havy weight oil on rotarys is not a good thing to do, by the time the motor warms up especialy, the lubrication while the oil is still thick and flows alot slower will be very poor because the oil injection in the motor will be minimal compare to lighter weight oils.

 

Ditto.

 

i run 5/50 castrol syntec. I have a seperate MOP tank with 2 stroke oil in it, so that isnt a problem for me.

I think one of the things you guys are missing is that 5/50 isnt 50 weight when its only partly warmed up. it doesnt switch between its cold and hot viscosities directly, it slowly changes, so if you are running colder, then the apparent viscosity wont be 50w, it will be 30 or 40 or whatever it is for that temperature.

anyway, im very happy with what i use, it keeps the car cooler, doesnt seem to coke up in the turbo, and lasts a long time. I'm positive that my engine and turbo are much saafer with this stuff than with any weight of dino oil.

pat

 

Yes, some oil is left over during each swap, but most oils are blends anyway (that and I doubt there's really enough left in the car to make a difference). It's kind of the same principle as mixing gas octanes.

 

I think you missed the part where some of us were saying that 20 w50 weight wasn't a good idea... I certainly see nothing wrong with 5w50!

BTW, since the temps I posted are being discussed, I feel obliged to mention that these are being achieved with dual 25-row oil coolers, NOT the stock setup. In fact, I think ANY modded FD should be running at least the stock dual cooler setup, even for street driving. Even my cruising temps were 35 to 40 degrees hotter with just the single stock cooler.

 

Yep, that's a good point to reiterate.

However, (not directed at you), I don't see an addition 35-40 degrees from that point breaking down 10w30 so quickly to justify anything heavier for the street.

 

I have an oil temp gauge, and the stock single oil cooler. In normal driving, after the car is warmed up, I see oil temps vary from around 200 to 250 degrees. This would be on an average 75 degree day. The higher temps would be around town, in city traffic.

 

oh bullshit

Mobil 1 15w-50 pours extremely well, even cold....it's really not as "thick" as you pundits are making it out to be (who have probably never used it)

like I said three times now, unless someone is willing to get a sample analyzed this is all worthless speculation....and I stand by my bet that 2k miles in a twin turbo rotary with the stock (single) oil cooler will result in significant viscosity degradation, at least 10-20% or more

 

When I switch to synthetic, should I change it then do it again after about 500 miles to ensure the majority of dino oil is out?

 

The percentige numbers you keep mentionning by your thoughts are right, have you done any kind of viscosity tests for this matter or you just guessing.

I rane 20W50 full synth. in my motor, seen no difference, and I came to conclusion that 20W50 might not be the right oil for street use as everyone else here is sayng.

I gave my opinion, but that's just what I beleive, after reading millions of threads here about it and I think 15W30 is just prefect for street use.

Till you come up with some real proof you can't realy put up numbers and vauch for them, you can of course have your opinion.

 

When you change it the first time, the majority of conventional oil will be out

I wouldn't worry about changing it again before it is normally scheduled.

EDIT: For what its worth, Tri Point Engineering recommends synthetic in a 20-50 weight.

 

^Is there anyone out there that has oil temps on a stock/near stock R1/R2 under similar conditions. Understanding that 'normal' is vague, I'm just curious on the effect (if any) of the second stock cooler.

 

Yeah, until the car reaches operating temp.



There has never been any reported failures due to a synthetic or conventional oil preference.





How do these threads keep getting started?

 

https://www.rx7club.com/showthread.p...4&page=1&pp=15

 

I'm surprised, yet at the same time I knew it all along...

 

Is there anything wrong with using 5W-30?

 

Read your owner's manual.

 

My comments really had nothing to do with the difference between synthetic or conventional... my comments were directly related to oil weights, and only weights.