Well I had been running 10W30 last summer here in MI and I thought I would change to 20W50 for this summer. Well I changed the oil(Valvoline VR1 oil) on Friday along with the plugs, and went from the stock set-up to stock 9s all around.

Anyway, I fired the 7 up, let it warm up and took it for a quick spin, nothing much. Only hit full boost once. Didn't notice any differences except the car idles a lot more smooth. So I was a happy individual.

Today, washed and waxed my car, and put on my re-surfaced chin spoiler (used dupli-color spray on bed-liner, looks superb and I highly recommend it) and then started it. Noticed now the revs are at 1050-1100k instead of 1200-1250K I used to see. The revs also used to not dip if I turned the lights on but now they do. Now with the lights on the revs usually go down to right around 1K. I know this is a typical symptom of the idle problems FDs have, and the tach also doesn't want to rev. down when in placed in neutral at around 1500 RPM on deceleration, just does it slowly. I am hoping this is can be fixed with a TPS adjustment but I haven't checked it out yet. The main thing that scared me is that my vacuum went from 19 at 1200ish RPM to 16 at just around 1100-1050 RPM. No it doesn't constantly fluctuate at idle just difficult to get a completely accurate measurement because it doesn't sit right at 16. When driving if I come to a complete stop it idles at 18 though, found that interesting. Also noticed I have a new small exhaust leak coming from the area of the rear inlet pipe for the rear turbo. So I'll go re-torque the DP bolts and see if that does anything, if not its gonna be a wonderful fix because its probably a shot gasket somewhere.

But can anyone give me reasons why my idle would go down along with my vacuum?

 

If your seals are not properly lubricated, they do not seal as well and you will lose compression (vacuum). Also, as your revs lower, your vacuum will decrease.

You should not be running 20w50 in Michigan. Especially with current temps. Mazda recommends 10w30. Most people using 20w50 are using it for racing conditions or consistent high heat conditions like Texas, South Florida, Arizona, etc. 20w50 is not viscous enough in more temperate climates. Change back to 10w30.

 

anything above 15-16in/hg is fine.

 

thanks for the advice, I will do that. I waited till now to change because of the viscousity issue, apparently still not appropriate though.

 

I've settled on using 10W40 during the summer and 10W30 during the winter for my street-only daily driver; always Valvoline. I key on the oil pressure after warm up with the engine at 3K RPM and switch oil viscosity to maintain an indicated 60 PSI using stock gauge/sender.

 

uhh....OK....you are right about the higher heat areas, but if you run the car hard, i PERSONALLY recommend the 20-50. i also use the valvoline vr1 oil that you mentioned, and as per my oil study, one that i posted ina thread here, found that that particular oil out lasted all the synth. and other mineral oils that i tried. less ash and less usage between teh oil change intervals....you do the figuring on that....

uhh, the fd in general does not like electrical loads, this has been known, so you think that the OIL is the reason that your idle fluctuates? not so....try again...20-50 is faaarrrrr more viscous than 10-30, so it has more resistance, and so on.....

i think that you should leave the oil in for the summer and then go to the thinner oil in the dead of winter....

IMHO....

 

thanks for the post. I've been thinking, in the summer its always 85+here so its not like its cold at all. I didn't think that the oil was causing the idle to change, I was just noting that it did after I changed the oil. Why this is, I don't know.

 

anyone else?

 

Since you just warmed the car up (rather than driving it around for a while, where you would get oil temps up to normal operating levels), what you're probably seeing is the oil pump working to circulate the thicker viscosity oil through the oil galleys and passages in the engine. The rotary engine doesn't exactly have a lot of rotating weight compared to bigger motors, and when you add all the other components (water pump, plus the belts that run the A/C compressor, air pump, and alternator) that contribute to what's called "parasitic drag" on the engine, then finally add the fact that the oil pump has to work a bit harder at idle to force the oil through all those small passages, then you end up with a slightly lower idle in your situation.

I'd be interested to see if your slightly lower idle remains after running the car hard for a while.

 

I would recommend NOT using 10w40. There are a few threads about it, but apparently 10w40 has additives which are not good for our cars.

There is probably a more techincal explaination than what I just wrote in one of the older threads but the consensus is to stay away from 10w40.

 

anyone else have experiences running 20W50 in a climate similar to Michigan during the summer months. I really think it will beneficial considering during the summer months it is consistantly 85+ and I do tend to run the 7 hard.

 

For those interested in finding out some real information on today's oils (not just a basic study on oil composition done many years ago-- many oil companies have changed their formulations since then), I'd suggest looking for the next two upcoming issues of Sport Rider magazine. We're doing a comprehensive two-part test on oils; the first part will deal with the basics of oil composition (similar to R Explicit's post a while back), what many of the additives are for, and what they mean for an engine. Granted, this information is geared towards motorcycles, but I believe R Explicit's posted article was pulled from a motorcycle website as well, and much of the information can be directly translated to a 13B motor; actually, all rotaries.

The second part, however, will consist of spectrographic analysis of a large portion of the top oils available today. This will show how much of these additives are in each oil, as well as other composition aspects that are important for oil performance in a high performance engine. Even more important will be a series of scientific tests to measure oil performance; some oils will go through a friction/wear test to measure their protective qualities on metal, in addition to a "shear" test which measures the oil's ability to maintain viscosity after repeated abuse from meshing gears (since motorcycles share their engine oil with the transmission). Correct me if I'm wrong, but isn't the engine oil in a rotary used to lubricate the gear teeth for the concentric shaft/rotors used for power transfer to the gearbox/transmission?

We will also do a dyno test to see if some of these full synthetic oils actually result in more horsepower at the rear wheel like some of them claim.

The first part (oil tech info) will be in the next issue (August), not the one on the newstands now (June). Don't worry, that cover date isn't what it seems; Sport Rider is a bi-monthly, so it comes out every two months, and the publishing company figures using that cover date will keep newstand hacks from throwing it away after a month, thus the "August" issue will actually go on sale in the first week of June. The analysis/testing portion will be in the October issue, which will be on sale in late July.

I know this sounds like a promotion for the magazine (well, I guess it is, for the most part), but I believe that this will be real, non-biased information that all rotary owners could actually use.

 

What I recall is that 10w40 was a frankenstein mixture to accomplish that weight and the 10w30 or 20w50 were more pure so to speak?

 

anyone else with experiances running 20W50 in the summer months in weather similar to what Michigan experiences.

 

Interestingly enough I just moved from Rochester Hills, MI to NJ. For at least 3 summers now I have used 15w-50 Mobil 1 Synthetic oil during late Spring and Summer time frame. No issues ever! FYI, I do run the car hard and I track the car several times a year. My mods are listed below.

And, yes it will get hot enough in MI during the summer--regardless of what people think.

 

Kento - do you guys distribute your mag in Canada? And also, do you guys have a website that you might be posting this info on?

 

Yes, the mag is distributed in Canada widely. In fact, my senior editor is a Canuck.

We won't be posting the results immediately on the website (they'll be posted later), as otherwise, why come out with the print mag? Sorry, but we gotta pay the bills somehow...

 

Makes sense Just figured if you didn't distribute it in Canada, I could find it some other way. I will definitely keep an eye out for it! Thanks for the info!