I searched this forum before I posted my question.

The subject is oil change intervals. I've seen various *mileage* based suggestions from a lot of this forum's members; 1K-6K-10K then every 10K, 5K-10K then every 10K, 4K-10K then every 10K, every 3K, every 4K, well you get the idea.

My question is this: are mileage based oil change intervals for our unique type of vehicles really appropriate? Depending on driving style and how often run in EV, one person's 5K miles might only run the ICE 50% of the time, which would mean 10K oil change intervals. Does this make sense?

Should I trust "the computer" to tell me when it's time to change the oil, or is that just a percentage based on 10K oil change intervals?

Should our vehicles have a gauge to tell us how many hours our ICE has run, and should not our oil change intervals be based on that?

Looking forward to an interesting discussion.

Thanks!
Bill

 

I suggested the "hours" run guage a while back we think alike. You didn't grow up on a farm did you? Thats what they do on farm equipment because it often idles (using the PTO etc.) and an odometer would be a pretty poor estimate of when it needed maintenance. Actually and "hours" running guage would be more accurate than the odometer on any car.

Thats one of the reasons they call city driving and taxi driving "severe conditions" in the manual. The odometer poorly represents the real number of hours those engines were running. In our case its the other way around and ours run less than what the odometer implies.

You'll hear some people suggest staying with 5,000 miles because they believe all the stopping and starting is hard on the engine, but I don't personally believe that. Dry stops and starts and long cranking is bad, but our engines are still warm... the oil is still up out of the oil pan and on the pistons, and they don't crank... they start in less than 0.5 seconds.

I personally think the 10,000 miles number is a good estimate by the engineers as to how many "hours" the engine has been running. Theoretically they designed the thing and should know what they are doing. Of course you can expect your dealers to hedge on the 5,000 mile side because they want to sell you more oil changes and filters.

 

Even if not displayed, "the computer" should base needing an oil change on hours of ICE usage, instead of odometer readings. I mean, I know how to read an odometer, and dividing by 10,000 isn't all that difficult; I can even do it without a calculator.

I agree that the Message Center should be able to display more useful info like hours 'on' for the ICE, a tach for the electric motors, temperature readings for both coolant systems, HV battery charge level, etc. I mean, it is a alphanumeric display; all it would take is a little software to display more useful things.

 

If I remember correctly, the manual recommends oil change to be at 10k miles or 200 engine hours. This is definitely tough to calculate since engine hours has absolutely nothing to do with how many clock hours the engine has run. It is just a count of revolutions displayed as an equivalent number of hours at a certain RPM. But, if you assume the engine runs at 2000 rpm at 50 mph then 10,000 miles would be 200 hours if the engine hour is based on 2000 rpm. If it is based on 2500 rpm then you are only at 160 hours and can go longer. There are also hour meters that count how long an engine was running (the "Hobbs" type meter) but they are useless for predicting maintenance requirements since they don't account for rpm. We rent our plane out by the hour on the Hobbs meter but maintain it by the tachometer hour meter. The Hobbs is always more time by at least 30%.

Like was said earlier, and what I have been posting since I got on this board, miles is a horrible measure of maintenance for an engine. If you ran a conventional transmission car for 5,000 miles in first gear that is a heck of a lot more wear than running it for 10,000 miles in overdrive gear.

They need to give us a better way to measure engine time. The Suburban I drive at work has engine hours right in the display. Probably took a computer programmer 3 minutes to write that program since all it does is count.

The oil change screen in the display is strictly a display of miles as a percent of 10,000. Forget to reset it and it still counts down. It has nothing at all to do with oil condition. Useless.

For me, every 4 or 5 thousand is my preferred interval. I may spend a little extra in oil but maintenance is cheaper than repairs.

 

Hi Ray... I was about to install an "Engine On" meter, as this would not be hard to rig... just find some wire that is only "hot" when the engine runs.

However, I REALLY like the idea of an RPM meter... especially since I RARELY exceed 2400 RPM!

Where do I get an RPM meter, and how would I wire that? Sounds like a very good idea to me!
-John

 

Not sure where you would acquire something like that. On the plane (as on some farm equipment I used to run), it is built into the tachometer. Not positive but I'm guessing the tach in the plane is cable driven, not electronic since the tach-hour meter is a rolling number type like an old speedometer.

Engine on time is probably a close second as far as keeping track of how much your engine has run.

 

You have one, its the Tachometer .

Seriously though can't you get engine RPM from the OBD system. Then all youd need is to record the Engine RPM. The times when it reads "0" the engine is off so you don't even really need the on/off feature. Sample each minute and add and you'd have a good guess of total engine revolutions.... and shouldn't that be the accurate way to know when to change oil? Of course we'd have to figure out how many revolutions was the right number (oh okay there is that nasty bit about the OBD interface details details...)

Still a new guage is a cool idea.

 

No, the tach only gives current RPMs, not life time total revolutions.

I am pretty sure the ICE computer knows each time the crank shaft is at TDC. It would just need to constantly count those, and base its "time to change the oil" suggestion each time that count passes some multiple.

Seems like nothing more than a 5 minute code change.

 

I'm not a computer programmer but I would guess that the code required to keep a count of an on/off input would be trivial. If you could find a place to mount a sensor that could count crankshaft revolutions, there would be no code - just a sensor and a counter.

I would think that an engine hour on these engines would use 2000 to 2500 rpm so every 24,000,000 to 30,000,000 revolutions would be oil change time if you go by the 200 hours from the book. At 60 mph for 10,000 miles at 2000 rpm you would do 20,000,000 revs. That is with absolutely no EV time so 10,000 miles is conservative compared to 200 hours.

 

Right but his message mentioned wanting a meter that read "RPMs" not revolutions. I was just trying to pull his chain a bit, I knew he meant a revolution meter.

He misspoke (miswrote?).... I've done it a million times myself!