the oil pressure is HIGHLY dependant on the oil temperature and condition of the oil. 5-10 degrees or 10% changes in oil viscocity will throw off how much oil pressure you have by a substantial amount.

edit-> add the oil filter differential pressure to the list of things you need to measure to make sense of things

edit 2-> thinking about it, the ambient air temp will effect how much the oil cools down in the oil coolers which will effect the backpressure

 

od they didnt cheap out, they took the path of least resitance. they had huge complaints in the past about fluctuating oil pressures (they werent the only ones) because people dont understand how to read a normal oil guage. it is easier to deal with the fewer complaints from folks abotu the on/off variety we have than to deal with the other.

 

Yes, especially since many people were not even thinking oil pressure when they looked at the gauge - they thought their oil level is fluctuating.

 

This is kind of a cop-out, Mazda advertises this car as a sports car. We all know it is a fine sports car and a sports car should have complete instrumentation. Oil pressure knowledge is something a sports car driver needs to know. I understand Joe Average may not know how to properly use a Oil Pressure gauge but that dose not mean you should delete it. Do you think Porsche use a idiot gauge?

 

correct me if im wrong but when your oil is running low youll get the oil light on the dash its red and annoying as hell

 

When that happens.... its already pretty low. I think that light comes on after you're down about a quart of oil (completely pulled that out of my ***). However even when I'm topped off I swear i see that light out of the corner of my eye and when I look down... its not on! I hate that damn light.

 

thanks a lot guys

 

Please tell me your knowledge of how to properly use an oil pressure guage...


Oil pressure guages are measuring back pressure and not flow. You can have high pressure and no oil flow (think blockage, cold oil, sludged oil), high pressure and too much flow (more pressure = more resistance), low pressure and no flow (break in the line somewhere), and low pressure and or low no flow (pump is broken or oil too thin from heat or fuel dilution). A real pressure guage will fail you in 1 out of the 3 cases just cases above that will hurt you just like the dummy guage will. Then for the back pressure to mean absolutely anything, you have to correct the oil temp, viscocity, ect to a standard condition and plot it as a function of rpm - which nobody is doing with a real pressure guage. Ironically, most real aftermarket guages have a dummy light just like our own dummy light and nobody pays attention to the damn guage until the light goes off.

A useful guage would be an oil flowmeter since thats what we are actually worried about. That would be a differential pressure guage across an orifice that you would then compare on a graph against the system backpressure and the oil pumps pump curve. It too would have to be corrected though to standard conditions to make sense out of it - but it would actually tell you if you had flow.

 

I disagree with your assumption. Mazda advertises this car to a certain demographic who, unfortunately, wants a cool looking dash rather than a functional one.

 

My pleasure, the gauge is an excellent indicator of possible problems with in your engine. It can give you advance warning of a problem before it strands you. The gauge can tell you if maybe you should use a heaver oil. It will tell you if your oil starving the engine in a turn. It can indicate a flow problem to be looked into. It can allow you set a bench mark that can be monitored over the life of the engine. It is not perfect but far better then an idiot light/gauge.

 

Is this a different demographic then the previous RX cars? I would say no, the 4 seats may sway that argument a bit but it seems most of us compared this car to 350Z, S2000, M3, STI, EOV ect...... a group of car that uses real instrumentation.

 

how can you you make any of those assumptions when a 10 degree difference in oil temperature can effect pressure by up to 10 psi?

 

I didn't mean that the gauge on my FC was useless. I just stated that I had no idea that the one that we have now is so much different from the one I had then. (I didn't know the FC, FD had real oil presure gauges) as opposed to the 8.

and yes I wish the 8 had my old presure gauge. It was verry reasurring to see that the oil presure fluctuated depending on engine load.

 

I am not commenting one way or the other whether the demographic is different from previous RX cars. I am saying that I believe that the current demographic is more influenced by "bling" than by functionality (at least where it shows) and that this is demonstrated by a number of marketing directed technical decisions about the RX-8. The instrument clutter is one of the more obvious ones.

IMHO, of course.

 

A little information is better then no information. As I stated it is not a perfect solution by any means but you can develop a bench mark at the least which will allow you to spot deviations from the norm.

As for "msrecant" I can see your point.

 

I agree with you on this, which is why I miss the RX-8 not having a real oil pressure guage. On my 1993 Miata I could not make an absolute statement about the oil pressure gauge's reading at any given instant in time. However, I quickly learned what was "normal" and could easily spot when the reading did not jive with the current condition of the car. The info was useful to me, even if it could not be used by someone driving my Miata for the very first time (excluding extreme readings).

 

that was awesome.

 

Zoom
Never thought of it that way. Makes sense. I guess a lot of people that are not really mechanically inclined did buy the car. Thanks for the fresh perspective. For the rest of us it is a little aggravating. I wish they would have , at least, offered the real gauges as an option. Still a great car and putting gauges in it increases bonding time.
Rot0r--the manuel says the oil pressure (not flow-- thats another ballgame)should be 50.8 at 3k with oil temp at 212F. My reading --repeated many times--showed a reading on MY car to be 48-49 at 3K with oil temp at 185,. 47-48 at 195F. I didnt think the pressure would go up any at 212F so I stopped. It was enough to convince me to change to a 5W/30. That placed the pressure in a nice range--just slightly above stock norms. Conclude what you may-I'm convinced.
Olddragger