Oil pressure gauges - pointless?
Discussion
Okay, so the oil pressure sender unit has gone kaput on my 355 and now registers high off the scale and stays there requiring a quick trip to the garage to get it replaced. This has also happened on my 911 previously.
So it's as the title says, are they a bit pointless? As far as I can see they basically only exist to go wrong! Logic being: the gauge tells you how much pressure you have. The only time you really have to worry is if it's zero at which point my 911 used to bleep at me to warn me and a light would come on (presumably the Fezza would do similar) anyway. By the time you'd registered that though, if the pressure genuinely was zero and not just a spurious reading, you'd have b*ggered you engine anyway. Only other reason to have it is so you can see when the oil is nicely warmed up before thrashing. But if you're smart enough to do that, you're also smart enough to know not to thrash a car for the first few miles or when it's not up to temp - appropriate thrashing oil pressure (I always use a nice hot idle reading) lags engine coolant temp by a couple of mins in my experience, but no more.
Therefore, if you have an oil pressure gauge and are smart enough to know how to use it, you don't need it really. And if you don't use it anyway cos you're thick and have no mechanical sympathy, why have it to start with??!!
So it's as the title says, are they a bit pointless? As far as I can see they basically only exist to go wrong! Logic being: the gauge tells you how much pressure you have. The only time you really have to worry is if it's zero at which point my 911 used to bleep at me to warn me and a light would come on (presumably the Fezza would do similar) anyway. By the time you'd registered that though, if the pressure genuinely was zero and not just a spurious reading, you'd have b*ggered you engine anyway. Only other reason to have it is so you can see when the oil is nicely warmed up before thrashing. But if you're smart enough to do that, you're also smart enough to know not to thrash a car for the first few miles or when it's not up to temp - appropriate thrashing oil pressure (I always use a nice hot idle reading) lags engine coolant temp by a couple of mins in my experience, but no more.
Therefore, if you have an oil pressure gauge and are smart enough to know how to use it, you don't need it really. And if you don't use it anyway cos you're thick and have no mechanical sympathy, why have it to start with??!!
In the 355 it surely is. Mine has a mind of it's own. Some days at motorway speed it can peg the dial like 140 psi. Other days it refuses to budge over 70 psi and some days does what it should do and works with rpm/heat cycling from idle 10-20psi to about 85psi. Have replaced sender with a new one, same result. I thought I noticed that it worked properly if the car idled for a short time before moving away, but I could be imagining this.
Ferrari have tested my car with a mechanical gauge and all hunky dory and they've told me it's due to the fact the tech goes back to the 70's and to just ignore it. Not sure what it's like in the newer cars. I just ignore it now and agree if there is no pressure thats when to be worried. The really old gauges worked better in my opinion the ones with a direct oil feed from the engine.
Lets not talk about the fuel gauge accuracy either.. lol or speedo accuracy..
Ferrari have tested my car with a mechanical gauge and all hunky dory and they've told me it's due to the fact the tech goes back to the 70's and to just ignore it. Not sure what it's like in the newer cars. I just ignore it now and agree if there is no pressure thats when to be worried. The really old gauges worked better in my opinion the ones with a direct oil feed from the engine.
Lets not talk about the fuel gauge accuracy either.. lol or speedo accuracy..
Edited by Lagerlout on Thursday 22 April 16:00
Lagerlout said:
Mario, I removed that from my original post because my memory is a bit dodgy. It might be the other way around. Will post back later. Maybe it is something to do with that 10mph headstart on all F speedos? lol
My understanding is that by European law a speedo is not allowed to under read. However, it is more than usual for them to completely and utterly over read and the faster you go, the bigger the over read.Edited by Lagerlout on Thursday 22 April 16:05
I guess the law doesn't stop a speedo from going kaput though.
I disagree too, my oil pressure guage has indeed been accurate (touch wood that I haven't jinxed it) and useful with one or two oil issues I've had.
Once you've learnt the variance in pressures depending on heat & rpm etc it will indicate to you if you're low on oil long before the warning light comes on (at which point, it's possibly too late).
I suspect it has saved me from a couple of rebuilds for what turned out to be minor issues to sort.
I realise I may be lucky with the accuracy of mine.
Oil temp is less useful but always of interest as it will help you read the pressure guage and I am grateful for every indicator that my baby is running happily!
Once you've learnt the variance in pressures depending on heat & rpm etc it will indicate to you if you're low on oil long before the warning light comes on (at which point, it's possibly too late).
I suspect it has saved me from a couple of rebuilds for what turned out to be minor issues to sort.
I realise I may be lucky with the accuracy of mine.
Oil temp is less useful but always of interest as it will help you read the pressure guage and I am grateful for every indicator that my baby is running happily!
Oil temp is very useful, especially knowing just when it's ok to exert right foot! Essential in an F.
Of course a pressure gauge is useful, I was being facetious, just I have seen and read about a lot of 355's with somewhat unique pressure readings. Owning a number of old cars I know exactly how pressure is affected by rpm, heat, relief valves etc. Some of the things the 355 sender/gauge can get up to the car cannot physically be doing is my point. Thats why it's odd, in some cases.
The instruments on pretty much every F I've ever been in have been wonky in some way accuracy wise. Normally the speedos but also the fuel gauges are notorious for being inaccurate.
Kind of boring though, but my S class used to be bang on to about 1mph at any speed. Bloody germans! lol
Of course a pressure gauge is useful, I was being facetious, just I have seen and read about a lot of 355's with somewhat unique pressure readings. Owning a number of old cars I know exactly how pressure is affected by rpm, heat, relief valves etc. Some of the things the 355 sender/gauge can get up to the car cannot physically be doing is my point. Thats why it's odd, in some cases.
The instruments on pretty much every F I've ever been in have been wonky in some way accuracy wise. Normally the speedos but also the fuel gauges are notorious for being inaccurate.
Kind of boring though, but my S class used to be bang on to about 1mph at any speed. Bloody germans! lol
For the cost of the sender (which is what usually goes), I like being able to keep an eye on things. An oil pressure gauge (which I randomly decided to install) saved the engine on my first car (ironically, the sender fitting had sheared at the block) so I now tend to drive with an eye on all the gauges periodically.
The Milfman said:
Once you've learnt the variance in pressures depending on heat & rpm etc it will indicate to you if you're low on oil long before the warning light comes on (at which point, it's possibly too late).
Hang on a sec! How does that work? Surely by the time the oil pressure changes enough due to oil running low (presumably meaning the scavenger pump is having trouble getting oil from the pan? Or have I misunderstood? Happy to be corrected!) you're oil level will be incredibly low anyway and should have been spotted during basic oil level checks?Cactussed said:
For the cost of the sender (which is what usually goes), I like being able to keep an eye on things
Very true, it is a bit of a peace of mind thing I guess. I'd be curious to know what the cost/benefit analysis works out as i.e. the total cost of having to install the sensor/gauge etc, and then redoing it when they go faulty, compared to how many engine rebuilds/replacements it saves.With a 996 911 for instance, I believe the sender unit plus fitting from an Indy is about £150 (and say every 911 has one done over its life, not unusual it would appear). Add another £50 because they also put one in when building the car which costs a little, so that equals £200. A new/reconditioned 996 engine is of the order of £7k. Therefore, it's only truly worth having if say more than 1 in 35 engines are stopped from failing due to oil pressure issues over the life of the vehicles.
I suspect that the fraction is in fact faaaaaar lower! I'm sure similar maths could be done for Fezzas!
Cactussed said:
Well, the sensor is about £100 for the 355. It's located on the back of the oil filter housing, so pretty easy to access and swap yourself, should the need arise.
Yeah, I was diagnosing it over the phone with a mechanic from Rardley yesterday while peering into the engine bay and asked whether it was a doable DIY job if they sent me the part. Apparently it's a little fiddly and it gets a little messy, and for the sake of driving 20 mins from work to there to get them to do it under warranty, I think I'll pass getting my hands dirty 
The Milfman said:
Oil temp is less useful but always of interest as it will help you read the pressure guage and I am grateful for every indicator that my baby is running happily!
I agree with that bit.... its a Ferrari, its tempremental, its expensive to repair. So peace of mind its not playing up is always good!Gassing Station | Supercar General | Top of Page | What's New | My Stuff