Mazda Miata: Gauging Oil Pressure

I agree, Karl. It should at least be marked with a "red zone"... although is there a low oil pressure warning light?

I didn't know the new models had a real oil pressure gauge. After '94 and up through the 2nd generation, it was a dummy gauge that only has "too low", "alright", and "too high" settings. Some people modify theirs to reflect reality but it's a pretty involved diy job.

I had a '91 that had a "real" gauge, but it never read as low as the one pictured. I'd say it would read 1/4 at idle and 5/8 at high rpm's. The car had 250,000 trouble free miles when I sold it, so I'd guess the oil pressure was OK.!

Karl,

Can you give an example of a "dumb" oil pressure gauge? Every car I've ever driven with a gauge, the needle rises and falls in sync with the revs. By "dumb" oil pressure gauge, did you mean "oil pressure warning light" (most cars that I have driven with a gauge was also equipped with a light).

7driver, a dumb oil pressure light is as functional as a warning light, but it looks like an oil pressure gauge.
 
It's a gauge on which the needle is ALWAYS at 50% unless something's wrong (in which case it falls to 0 or jumps to 100). It doesn't fluctuate with the throttle or revs, just stays on 50%.

Carlisimo, what car (or cars) is equipped with a gauge that behaves like this? I've not seen a car with a a gauge that does this.

'95-'05 Miata. Some Fords too; the only one I know of for sure is the Ranger (presumably from around the same years as the Miatas with idiot gauges).

Most GM vehicles have real-time oil pressure gauges too. Both my '02 Corvette and my '99 Suburban diesel have real time oil pressure gauges that fluctuate with both engine RPM and with engine oil temperature (colder oil is thicker and runs higher pressures, which gradually goes down as the oil heats up). The difference is both my GM vehicles have actual numbers on the oil pressure gauges, so I know at idle it's running 34 psi, and 45 psi at cruising speed. On the Corvette I can also pull up a digital number reading of the oil pressure on the information console, in addition to the analog gauge, as well as pull up actual engine oil temperature. Oil temperature is just as important as pressure on a performance car that may see track time. I think all performance cars, and trucks that do major towing, should have oil temperature gauges too.

my truck did that too, when i first got it i freaked out thinking i had a problem on my hands.

My GM truck seems to have a "real" oil pressure gauge as well... in that it flucuates between idle, and changes with RPM's - high RPM produce a higher oil pressure and cruising keeps a steady needle, but floor it and change gears, the oil pressure gauge aslo repsonds....
 
On the other hand though, I have driven many Fords, and the ones that have had oil pressure gauges flip immediately to the center mark and stay there... I think that is what counts as a "dummy" gauge.
 
I also used to manage a lube shop and I always remember Fords having this type of gauge. The needle would stay at the "low" mark for a few seconds and then flip to the center mark. GM"s that had gauges would slowly rise to the mid point between low and halfway. These are the only ones that I particularly remember. Most foriegn cars had idiot lights only, as well as domestic sedans. Chrysler as far as I can remember had "real" gauges too, but I don't specifically recall.

Year roar, I would like all of the gauges to have actual numbers versus a "L" or "C" or "H" like the Miata has. I'm not sure how much more it costs a manufacturer to have calibrated gauges, but you'd think once they design the oiling system and certify the oil pump that will be used they should know what the engine's oil pressure is (all that pre-production testing has to produce some kind of data). After that they should just mark the production car gauges with the appropriate numbers and call it day.
 
FYI, my 1970 GTX has numbers on the oil pressure (and temp and alternator) gagues, but both the temp and oil gauges are "dumb" (i.e. they don't change with RPM, but will generally rise or drop after extended idling or highway cruising). My Challenger's oil pressure gauge is both "dumb" and not numbered. Of course none of its gauges on those cars are very helpful. The fuel gauges on both only go to 7/8ths -- even when gas is spilling out of the fill tube.

I had the same oil pressure worry about my 2006 Miata. I made the dealer write it in the service request so if something blows up it has been documented. But the owners manual does state the acceptable range is between the lowest mark and the highest, so that's some comfort. Still, I'd have preferred some numbers on the gauge.

Believing that "L" is 0 psi and "H" is 100 psi which appears to be a reasonable assumption of a linearly calibrated gauge and with a 100 psi range and with 16 hash marks minus one after L and one before H would indicate 5 psi per mark and including the missing L mark the photo would be showing 10 psi at idle which is probably about right and in center between the two marks would be 47.5 psi which is also reasonable for cruising in that this is not a race prepped engine.
                         CHRIS